EXERCISE MACHINE

Abstract

The invention relates to an exercise device comprising a biasing element intended to be moved by the force of a user, an electric actuator (1) comprising a mobile part, the biasing element being connected to the mobile part and the biasing element being able to move the mobile part, a computer (12) able to generate a control signal for the electric actuator, an acceleration sensor coupled to the mobile part in order to measure the acceleration of the mobile part and to transmit the measured acceleration to the computer (12), the electric actuator being able to exert a force on the biasing element by way of the mobile element in response to the control signal, characterized in that the computer (12) is able to generate the control signal depending on the measured acceleration such that the force exerted by the electric actuator (1) includes a contribution of artificial inertia substantially proportional to the acceleration measured by the acceleration sensor.

Description

The invention relates to the field of exercise machines. More particularly, the invention relates to the field of machines with electric motor drive designed to develop or reconstitute the musculature of a user and being used in particular for sport training or for the reeducation of the muscles of a user.

Among the muscle exercise machines, there are in particular weight machines and inertia machines.

The weight machines operate on the principle of weights made of cast iron or another material that a user moves by imparting a force to counter the weight of the cast iron masses. These machines are notably presses, free weights, guided load appliances, etc.

The inertia machines operate differently. These consist, for example, in setting a disc of cast iron in motion about a rotation axis. The user must therefore impart an adequate force to overcome the inertia of the machine. Some machines operate with the principle of setting a fluid in motion with a system of fins. Although the fluid set in motion has an inertia, in these machines the user must primarily overcome the viscous friction induced by the fluids. Other machines use the principle of the eddy current system to generate these viscous frictions. These machines that produce viscous frictions are notably the machines of rowing machine or exercise bicycle type.

According to one embodiment, the invention provides an exercise device comprising

• • a load element intended to be displaced by the force of a user,
  • an electric actuator comprising a moving part, the load element being linked to the moving part and the load element being able to displace the moving part,
  • a computer able to generate a control signal for the electric actuator and
  • an acceleration sensor coupled to the moving part for measuring the acceleration of the moving part and for transmitting the measured acceleration to the computer,
  • the electric actuator being able to exert a force on the load element via the moving part in response to the control signal,in which the computer is able to generate the control signal as a function of the measured acceleration in such a way that the force exerted by the electric actuator includes a contribution of artificial inertia substantially proportional to the acceleration measured by the acceleration sensor.

According to one embodiment, the computer is able to generate the control signal as a function of the measured acceleration and a coefficient of proportionality and the computer is able to vary the coefficient of proportionality as a function of at least one parameter chosen from the position, the speed and the acceleration of the moving part.

According to one embodiment, the computer is able to generate the control signal in such a way that the force exerted by the electric actuator includes a contribution of additional load exhibiting a predetermined direction.

According to one embodiment, the computer is able to generate the control signal in such a way that the contribution of artificial inertia is oriented in the same direction as the contribution of predetermined direction when the measured acceleration is in the direction opposite the contribution of predetermined direction.

According to one embodiment, the computer is able to generate the control signal in such a way as to cancel the contribution of artificial inertia when the measured acceleration is in the same direction as the contribution of predetermined direction of the electric actuator.

According to one embodiment, the link between the load element and the moving part includes a speed reducer for gearing down the force of the motor. Generally, such a reducer generates an additional real inertia for the user who actuates the load element. According to one embodiment, the contribution of artificial inertia exerted by the electric actuator may compensate all or part of the additional real inertia generated by the reducer.

According to one embodiment, the device comprises a speed sensor suitable for measuring the speed of the moving part and the computer is able to generate the control signal in such a way that the force exerted by the electric actuator includes a contribution of viscous friction substantially proportional to the speed measured by the speed sensor.

According to one embodiment, the electric actuator is a linear motor.

According to one embodiment, the electric actuator is a rotary motor in which the moving part comprises a rotor of the rotary motor.

According to one embodiment, the acceleration sensor comprises:

• • a position coder coupled to the moving part for measuring the position of the moving part, the position coder generating a position signal,
  • shunt elements suitable for shunting the position signal to determine the acceleration of the moving part.

According to one embodiment, the exercise device is selected from the group comprising rowing machines, exercise bicycles, lifting bars and guided load appliances.

According to one embodiment, the moving part comprises a rotationally mounted motor shaft, the motor shaft is coupled to a reducer, a pulley is coupled to the reducer, a cable is fixed to the pulley at a first end of the cable, the cable is fixed to the manipulation element at a second end of the cable and the cable is able to be wound on the pulley.

According to one embodiment, the exercise device comprises a human-machine interface enabling a user to set a coefficient of proportionality between the measured acceleration and the computed contribution of artificial inertia.

According to one embodiment, the computer is able to compute the force to be exerted in such a way that the force to be exerted by the electric actuator includes a contribution of additional load exhibiting a predetermined direction, the human-machine interface enabling a user to set the contribution of additional load independently of the coefficient of proportionality.

According to one embodiment, the human-machine interface enables a user to set the contribution of additional load to a zero value.

According to one embodiment, the load element can be displaced in a vertical direction and the computer is able to compute the force to be exerted in the absence of force exerted by the user, in such a way that the force to be exerted by the electric actuator includes a default contribution of load compensating a specific weight of the load element without causing any spontaneous displacement of the load element in the absence of force exerted by the user.

According to one embodiment, the invention also provides a method for controlling an exercise device comprising:

• • measuring the acceleration of a moving part of an electric motor in response to the force of a user exerted on a load element linked to the moving part,
  • generating a control signal as a function of the measured acceleration and controlling the electric actuator with the control signal in such a way that the force exerted by the electric actuator on the load element via the moving part includes a contribution of artificial inertia substantially proportional to the measured acceleration.

One idea on which the invention is based is to simulate, on an exercise machine, when the machine is being used by a user, an inertia that is different from the real inertia of the exercise machine, using an electric actuator.

One idea on which the invention is based is to devise a machine which makes it possible to vary the weight and the inertia independently of one another.

Some aspects of the invention start from the idea of simulating, on the exercise machine, an additional weight using the electric actuator.

Some aspects of the invention start from the idea of simulating, on the exercise machine, an additional friction using the electric actuator.

Some aspects of the invention start from the observation that combining the exercises of “inertia” type characteristic of the inertia machines and the exercises of “weight” type characteristic of the weight machines in a single machine allows for a significant space saving and a less costly investment.

Some aspects of the invention start from the idea of generating additional inertia forces in certain phases of a muscle exercise performed by the user and of cancelling these inertia forces in the other phases of the muscle exercise.

Some aspects of the invention start from the idea of generating inertia forces without fixed load to create muscular stresses specific to the reversal of the movement of a mass launched on a substantially horizontal trajectory, notably the reversal of the movement of a runner.

The invention will be better understood, and other aims, details, features and advantages thereof will become more clearly apparent during the following description of a number of particular embodiments of the invention, given solely by way of illustration and in a nonlimiting manner, with reference to the attached drawings.

In these drawings:

FIG. 1 is a schematic representation of an exercise device including a motor.

FIG. 2 is a schematic representation of the control system of the motor represented in FIG. 1.

FIG. 3 is a graph of the position and acceleration as a function of time of the handle described in FIG. 1 corresponding to a manipulation by the user.

FIG. 4 is a graph of the force exerted by the motor upon a manipulation of the device of FIG. 7.

FIG. 5 is a graph of the force exerted by the motor upon the manipulation of the device in accordance with FIG. 3 corresponding to a first type of exercise.

FIG. 6 is a graph of the force exerted by the motor upon the manipulation of the device in accordance with FIG. 3 corresponding to a second type of exercise.

FIG. 7 is a schematic representation of a variant of the exercise device.

FIG. 8 is a schematic representation partially in cross section of an exercise device including a motor according to another embodiment.

FIG. 9 is a functional schematic representation of a control system for the motor represented in FIG. 8.

FIG. 10 is a schematic representation of an exercise for reversing the movement of a runner.

FIG. 11 is a graphic representation of the operation of a hysteresis comparator that can be used in the control system of FIG. 9.

FIGS. 1 and 2 illustrate an exercise device in which control methods according to the invention can be implemented. Referring to FIG. 1, the exercise device comprises an electric motor 1 which can rotationally drive a shaft 2 and exert a torque on the shaft 2. A pulley 3 is tightly mounted on the shaft 2. A cable 4 is fixed at its first end in the groove of the pulley 3. This cable 4 can be wound in the groove around the pulley 3. The second end 5 of the cable has a handle 6 fixed to it, via which a user can influence the device with his or her muscular force when practicing muscular exercises.

The motor 1 comprises a position coder 10 which measures the position of the motor shaft 2. The position is transmitted to an electronic board 7 in the form of a position signal 9. This electronic board 7 is designed to receive this position signal and uses the position signal 9 to generate a control signal. By virtue of this control signal, the electronic board 7 controls the torque generated by the motor 1 to control the force exerted by the motor 1, which is transmitted to the handle 6 via the pulley 3 and the cable 4. For this, the electronic board 7 transmits the control signal to the motor 1 via the connection 8. This control signal is received by a power supply member incorporated in the motor 1 which, from this control signal, supplies a certain current to the motor 1. The current supplied by the power supply member thus induces a torque on the moving part 2 and therefore, via the pulley 3 and the cable 4, a force on the handle 6. The force exerted by the motor 1 is substantially proportional to the current supplied by the power supply member to the motor 1.

Numerous control methods can be implemented in such a device in order to produce different muscular stresses. A first example is to simulate the presence of a predetermined mass suspended on a cable, namely that the motor torque exerts on the handle 6 a load that is constant in terms of direction and intensity.

When a user manipulates the handle 6 during an exercise, the user opposes the force of the motor 1 using his or her muscular force. For example, in an exercise that can be practiced with this device, a user is positioned above the device and performs a pulling action on the handle 6 from a low position to a high position using his or her hands. In this upward displacement, the user must overcome the force directed downward exerted by the motor 1 on the handle 6. When the handle 6 arrives in the high position, the user performs the reverse movement and returns the handle 6 to the low position while still being constrained by the same force which is subjected in the same direction by the motor 1. In the descent, the user accompanies and slows the downward displacement of the handle. The exercise device thus simulates a mass that has to be alternately raised and lowered by the user.

During this exercise, the position signal is transmitted continuously to the electronic board 7 which computes and continuously transmits the corresponding control signal to the motor. Thus, the device controls the force generated by the motor 1 throughout the exercise.

However, there may be a slight offset between the moment when the coder transmits the position and the torque exerted by the motor 1 because of the response time of the motor 1 to the control signal and the response time of the electronic board 7.

Referring to FIG. 2, the control means of the motor will now be described more specifically with reference to a second example.

The electronic board 7 here comprises a microprocessor 20. A position coder 10 measures the position of the shaft of the motor 2, this position is encoded into a position signal which is transmitted via the connection 38 to the microprocessor 20. Thus, in one embodiment, this measurement can be emitted every 30 ms and preferably every 5 ms. In this microprocessor 20, the position signal is transmitted to a shunt member 13 via the connection 18. The shunt member shunts the position signal thus generating a speed signal which is transmitted to a second shunt member 14 via the connection 15. The second shunt member shunts the speed signal thus generating an acceleration signal. The acceleration signal is transmitted via the connection 17 to a computation module 12. Moreover, the position signal and the speed signal are respectively transmitted to the computation module 12 via the connections 11 and 16. The computation module 12 computes the control signal to be supplied to the motor and transmits it to the motor via the connection 19.

More specifically, the control signal is computed from the acceleration such that the force exerted by the motor 1 on the handle 6 includes the load directed downward and a predetermined artificial inertia.

For this, the computation module 12 takes into account the aggregate of the torque exerted by the motor 1 and the inertia of the rotating parts of the device liked to this motor that are the shaft 2, the pulley 3, the cable 4 and the handle 6.

In effect, when a user manipulates the handle 6:

m _γ ×↓=F _m +F _Σ  (1)

in which F_Σ is the force exerted by the user on the handle 6, F_m is the force exerted by the motor 1 on the handle 6 and controlled by the computation module 12, m_γ is the inertia of the moving parts brought to the handle 6 and the mass of the handle 6 and γ is the acceleration of the handle 6.

The equation (1) corresponds to the fundamental principle of dynamics applied to a translational system. However, a person skilled in the art will understand that the torques exerted on a rotational system can be modeled in a similar manner.

The force exerted by the motor F consists of two components induced by the control signal: a fixed component representing the load and a component proportional to 15 the acceleration y _E which represents the artificial inertia. Thus:

F _m =F _ch +F _i  (2)

in which the force F_i is defined as a function of a coefficient of proportionality k:

F _i =−k×γ  (3)

The coefficient k is a parameter which is programmed in the computation module 12.

The equation (1) can be rewritten:

(m_γ+k)×γ=F_ch+F_s  (4)

In this way, if the coefficient of proportionality k used to produce the control signal is negative, namely −m_γ<k<0, the device simulates an inertia that is lower than the real inertia of the device, that is to say the inertia of the rotating parts of the device. If the coefficient of proportionality k is positive, the device simulates an inertia that is greater than the real inertia of the device.

The user, through a user interface that is not represented, can modify the values of the fixed component F_ch and of the proportionality factor k and thus determine the type of effort with which he or she wants to exercise. Thus, it is possible to independently vary the load of the inertia. A wide range of muscular exercise types can therefore be offered to the user.

The user interface is connected to the computation module 12 and is able to receive data concerning the position, the speed, the acceleration, or information computed from these data, for example the effort supplied or the power dispensed. These data and information are computed by the computation module 12 from the acceleration, speed and position signals transmitted to the computation module 12 respectively via the connections 17, 16 and 11. With these data and this information, the user interface can sensorially stress the user by displaying this information. The user can in this way follow the level of his or her effort in his or her physical exercises. However, these stresses may be of different natures, sound stresses can for example be envisaged. Moreover, the user interface comprises control members enabling the user to vary the values of the fixed component and of the proportionality factor k, preferably independently of one another. These control members are, for example, buttons on the user interface corresponding to predetermined pairs of fixed component F_ch and proportionality factor k. Theses pairs thus define a number of exercise types. A storage member, for example a memory in the computation module 12, makes it possible to store this information and data. Through this storage, the user can follow the trend of his or her performance levels over time.

Referring to FIGS. 3, 5 and 6, a number of particular examples of exercises which can be produced by the device described above will be described.

FIG. 3 represents the position of the handle 6 along the axis z of FIG. 1 and the acceleration of the handle 6 as a function of time in handle pulling stresses represented with reference to FIG. 1. The broken line curve 21 represents the position of the handle which is measured by the position coder 10. The continuous curve 22 represents the acceleration corresponding to the position curve 21. By convention, the axis z is oriented downward in FIG. 1. The point 24 of the position curve 21 therefore corresponds to the moment when the handle 6 is in the low position and the point 23 corresponds to the high position of the handle.

For the purposes of illustration between the point 23 and the point 25, the position curve 21 is substantially sinusoidal. Thus, the acceleration also forms, along this period, a sinusoidal curve. Consequently, the position curve is no longer sinusoidal and therefore the acceleration is no longer sinusoidal.

FIG. 5 represents the force exerted by the motor 1 against the user as a function of time for the same time interval as FIG. 3. The curve 28 is constant at the level of a threshold 26. In practice, FIG. 5 corresponds to a first exercise in which the computation module supplies a control signal to the motor in such a way that the force exerted against the user is constant in time. For this, the computation module produces a control signal inducing a force that has a load component equal to the threshold 26 and a zero inertia component. In this exercise, the user therefore works solely against a fixed load and the real inertia of the system.

FIG. 6 represents a second exercise which partially uses the principle of the first exercise described with reference to FIG. 5. The curve 40 represents the force generated by the motor 1 during this exercise. It comprises two phases: a high phase 31 during which the curve is constant at the level of the threshold 27 and a low phase during which the curve adopts the form of the acceleration curve at the level of the threshold 27. In practice, the user is subjected to a load force corresponding to the threshold 27 when the measured acceleration is positive, that is to say, here, during high phases 31 of the manipulation of the handle in which the handle is close to its high position 23. The user is, however, subjected to an additional inertia force oriented in the same direction as the load force when the measured acceleration is negative, that is to say during a low phase 29 when the handle arrives in the low position 24 and the user slows down the descent and then accelerates to perform a pulling action on the handle toward the high position 23. This low phase corresponds to the phase 30 during which the acceleration is negative. In this way, the user is subjected to an additional artificial inertia when he or she arrives at the low position and wants to raise the handle again toward the high position, that is to say at the moment when his or her muscular stress is most intense. Thus, the exercise device makes it possible to produce an additional stress which works against the user in a reversal of the direction of the movement of this user.

For the implementation of the second exercise, the computation module 12 applies a coefficient of proportionality k determined as follows:

If γ>0, k=0  (5)

If <0, k=+k₀, i.e. k>(6)

in which k₀ is a predetermined positive constant.

The exercises described above are given by way of illustration. In particular, the computation module can control the coefficient of proportionality k in many ways. As an example, the computation module can vary the coefficient of proportionality as a function of the position or the speed of the handle. Thus, in a variant, the exercise device produces a component of additional inertia when the handle reaches a certain position. In a variant of the exercise device, this component of additional inertia is added when the speed is in a particular direction. In this way, a multitude of advantageous exercises for muscular development can be produced. This notably makes it possible to stress the muscles of the user more intensely when they are in a particular position.

In a variant of the device presented in FIG. 1, the motor shaft 2 is linked to a speed reducer that has a reduction ratio r. The presence of such a reducer makes it possible to generate relatively significant forces while reducing the size of the motor, in the interests of miniaturizing the device. The pulley 3 is fixed onto an output shaft of the reducer. In this variant, the presence of a reducer greatly increases the real inertia of the moving parts of the motor 1 imparted to the handle 6. The real inertia of the device is also increased by the inertia imparted from the rotating parts of the reducer. The inertia of the motor and of the reducer imparted to the output of the reducer J_tot can be written:

J _tot =J _red +r ² J _mot  (7)

with the inertia of the reducer J_red and the real inertia of the motor J_mot. Thus, if the reduction ratio r is high, the real inertia of the system is greatly increased. Thus, the use of a negative proportional factor k makes it possible in this variant to compensate all or part of the inertia induced by this reducer. This compensation is all the more accurate when the acceleration which is measured to generate the artificial inertia force is the acceleration of the motor shaft 2, such that this measurement takes into account the effect of the reducer, an effect which consists in increasing, by the ratio r, the acceleration on the motor shaft 2 relative to the acceleration exerted on the handle 6.

The very simple exercise device described with reference to FIGS. 1 and 2 is given by way of illustration, but the invention is in no way limited to this type of exercise device. Notably, the invention can be adapted to any type of exercise machine stressing any part of the body. As an example, the invention can be adapted to form a device of rowing machine, exercise bicycle or lifting bar type.

With reference to FIG. 7, an exercise device 50 is represented for exercising the muscles of the arms in pulling and pushing modes, in which control methods according to the invention can be implemented.

The device 50 comprises two levers 53 which can be displaced alternately forward and backward by a user. The levers 53 are each coupled to an electric motor 54 which is controlled by the control device 55. According to one embodiment, the motors 54 are controlled in such a way as to generate a force represented by the curve 33 of FIG. 4. For the purposes of simplification, the rotary movement of the levers is approximated as a linear movement along the axis x.

Thus, FIG. 4 represents the effort working against a user in the context of the exercise device represented in FIG. 7. The curve 33 represents the force generated by the motor and presents a value proportional to the acceleration curve 30. It is assumed that a user performs stressing actions on the lever 53 in such a way that the measured position and the acceleration are the same as in FIG. 3, the axis x here replacing the axis z. In this type of exercise, the control device 55 submits a control signal to the motors 54 which does not induce any load component. Only an artificial inertia component is produced by the motors 54. Thus, the effort undergone by the user is proportional to the acceleration and therefore corresponds to a simulated inertia without load which is greater than the real inertia of the device.

This type of stress with an artificial inertia with no additional load is also advantageous in an exercise machine stressing the leg muscles. In practice, the muscular stress produced by the motor when it is controlled in this way corresponds substantially to the muscular stress needed to reverse the movement of a runner on a horizontal terrain. Such an exercise is illustrated in FIG. 10.

In FIG. 10, the runner 34 is initially running at high speed in the direction of the axis x, as schematically represented by the speed vector 35. At the end of the exercise, the runner 34 is running at high speed in the direction opposite to the axis x, as schematically represented by the speed vector 36. During the exercise, the runner 34 has therefore had to slow down his or her movement to a stop, occurring for example at the point x0, and then speed up again in the other direction. The muscles of the runner 34 have therefore been stressed during this exercise essentially to overcome the inertia of the runner him- or herself, oriented on the axis x. Since the force of gravity is perpendicular to the movement, it does not create any particular muscular stress in this exercise, that is to say that the muscular stress specific to the exercise is a pure inertia stress. The exercise machine programmed to produce this type of stress is all the more advantageous when this reversal of direction situation is very commonplace in ball sports, for example rugby or football.

Similarly, a control program associating the artificial inertia force with a constant load makes it possible to produce a muscular stress similar to accomplishing the same exercise on a sloping terrain.

A device that makes it possible to simulate an additional viscous friction force will now be described. The device is similar to the device described with FIG. 7 and comprises a microprocessor that has the same structure as the microprocessor 20 of the control system described in FIG. 2. The force exerted by the motor here comprises three components. The first two components correspond to the load component and to the inertia component described above. The third component is a viscous friction component. Thus:

F _m =F _ch +F _i +F _fv  (8)

in which the force F_fv, corresponding to the viscous friction component, is defined as a function of a coefficient of proportionality and as a function of the speed v of the handle:

F _fv =k ₂ ×v  (9)

The speed v is determined by the computation module 12 using a speed signal which is transmitted to the computation module 12 via the connection 16.

Thus, when the user displaces the levers in one direction, the motor generates a torque on the lever comprising the component of viscous friction proportional to the speed of displacement of the lever in addition to an inertia component. This viscous friction component causes an additional stress which opposes the direction of movement of the user. In this way, the device simulates a viscous friction that can be produced by a machine comprising a fin system.

The coefficient k₂ can be a constant stored in the memory of the microprocessor 20. In the same way as the inertia component, the computation module 12 can control the coefficient of proportionality k₂ in multiple ways. By way of example, the computation module can vary the coefficient of proportionality k₂ as a function of the position of the handle.

Referring to FIGS. 8 and 9, there now follows a description of another exercise machine 60 using an electric motor. The machine 60 has a form relatively similar to a weight machine known as a squat machine. However, it can provide a much wider range of muscular stresses.

The structure of the machine comprises a metal plinth 61 placed on the ground, shown in cross section in FIG. 8, and a guiding column 62 fastened vertically to the plinth 61. The top surface of the plinth 61 constitutes a platform 68 intended to accommodate an athlete, for example in a standing position as illustrated by a broken line. A carriage 63 is mounted to slide on the column 62 by guiding means that are not represented, so as to be translated vertically along the column 62. According to one embodiment, the carriage 63 is a four-sided structure which completely surrounds the column 62, both having a square section. The carriage 63 bears gripping rods 69 which extend over the platform 68 and are intended to be engaged with the athlete, for example at the level of his or her shoulders, arms or legs depending on the desired exercise.

A transmission belt 61 is mounted in the column 62 and extends between an idler pulley 65 mounted to pivot at the top of the column 65 and a driving pulley 66 mounted to pivot in the plinth vertically in line with the column 62. The belt 64 is a toothed belt which performs a closed loop reciprocal travel between the pulleys 65 and 66 so as to be coupled without slip to the driving pulley 66. The carriage 63 is securely attached to one of the two branches of the belt 64, for example by means of rivets 67 or other fastening means, in such a way that it is also coupled without slip to the driving pulley 66, any rotation of the pulley 66 being translated into a vertical translation of the carriage 63. Preferably, the belt 64 is formed from a toothed band of AT10 type whose two ends are fixed to the carriage 63, in such a way as to close the loop at the carriage 63.

A motor set 70 is housed in the plinth 61 and coupled to the driving pulley 66 via a speed reducer 71. More specifically, the speed reducer 71 comprises an input shaft 72 coupled without slip to the motor shaft of the motor set, which is represented in more detail in FIG. 9, and an output shaft 73 which bears the driving pulley 66. The speed reducer 71 imposes a reduction ratio r between the speed of rotation w1 of the shaft 72 and the speed of rotation w2 of the shaft 73, namely w1/w2=r. According to embodiments, the reduction ratio r is chosen between 3 and 100, and preferably between 5 and 30.

The machine 60 also comprises a control console 74 which can be securely attached to the plinth 61 or independent thereof. Furthermore, an electrical power supply cable 75 exits from the plinth 61 to be connected to the electrical network. The machine 60 does not require an exceptional electrical power supply and can therefore be powered by an everyday domestic network.

FIG. 9 represents more specifically the motor set 70 and its control unit 80, which is also housed in the plinth 61. The motor set 70 comprises an electric motor 76, for example a self-driven synchronous motor, and a current regulator 77 which controls the power supply current 78 to the motor 76.

It will be recalled that the self-driven synchronous motor exhibits a constant rotor flux. This flux is created by permanent magnets or windings mounted in the rotor, while the variable stator flux is created by a three-phase winding making it possible to orient it in all directions. The electronic control of this motor consists in controlling the phase of the current waves so as to create a revolving field, always 90° in advance of the field of the magnets, in order for the torque to be maximal. In these conditions, the motor torque on the motor shaft 2 is proportional to the stator current. This current is accurately controlled in real time by the control unit 80 via the current regulator 77.

For this, the control unit 80 comprises a low-level controller 81, for example of FPGA type, which receives the position signal 83 from the position coder 84 of the motor shaft 2 and performs real-time computations from the position signal 83 to determine the instantaneous values of the position, the speed and the acceleration of the motor shaft 2. The position coder 84 is, for example, an optical device which supplies two square wave signals in quadrature according to the known technique.

The high-level controller 82 comprises a memory and a processor and executes complex control programs on the basis of the information supplied in real time by the low-level controller 81. Possible control programs have been described above with reference to FIGS. 3 to 6.

The control console 74 is linked to the high-level controller 82 by a TCP/IP link 85, wired or wireless, and comprises an interface enabling the athlete or his or her trainer to select prerecorded exercise programs or to set the parameters of such a program precisely and in a personalized manner. In the example represented, the interface is a touch screen 86 which comprises a cursor 87 for setting the value of the load F_ch, along a predetermined scale, for example 0 to 3000 N, and a cursor 88 for setting the value of the coefficient k along a predetermined scale, that is to say the artificial inertia force F_i.

Depending on the exercise program being executed, the high-level controller 82 processes the information supplied in real time by the low-level controller 81 and computes the instantaneous torque that has to be exerted by the motor set 70. The low-level controller 81 generates a control signal 90 corresponding to this instantaneous torque and transmits the signal 90 to the current regulator 77, for example in the form of an analog control voltage varying between 0 and 10 V. As a variant, a CAN digital interface may also be used.

The control programs that make it possible to simulate different exercises can be many. Preferably, regardless of the detail of the program, it is always the athlete who controls the machine 60 and the machine 60 which reacts to the stress exerted by the athlete on the gripping bars 69. For this, it is preferable for the machine 60 to be able to react rapidly to the changes of direction imposed by the athlete, despite the frictions which inevitably exist in such a mechanical system.

For this, according to one embodiment, the high-level controller 82 implements a friction compensation algorithm which will now be explained.

The mass of the carriage 63 is denoted mc. Fc=mc.g denotes the force that the motor 76 must impose on the belt 64 to compensate the weight of the carriage 63 without the user supporting any load. The algorithm uses parameters a and b defined by the fact that if the motor 76 applies Fc+a the carriage 63 is at the limit of the movement in the positive direction, upward, and if the motor 76 applies Fc−b the carriage 63 is at the limit of the movement in the negative direction, downward. These parameters a and b can be measured by trial and error. The algorithm governs the transition from the force Fc+a to the force Fc−b in the case of a change in the direction of the stress exerted by the user. The algorithm applies laws which use the linear speed v of the carriage 63 and a coefficient kf, namely:

Fch0=Fc+kf.v  (10)

Fc−b<Fch0<Fc+a  (11)

in which Fch0 designates the force imposed by default on the belt 64 by the motor 76, namely the value which is applied when the cursor 87 is placed on the zero graduation. In other words, if the cursor 37 is placed on the 3000 N graduation for an exercise program for exerting this load alternating in both directions, and the carriage 63 weighs 60 kg, the electric motor will in fact exert a force of approximately 3600 N in the upward direction and 2400 N in the downward direction.

Thus, the higher the coefficient kf, the quicker the machine reacts to the changes of direction imposed by the user. Beyond a certain limit, a very strong reactivity would entail a frequency-domain filtering of the speed measurement, for example of first order low-pass type.

According to the program selected, for example, when an artificial inertia force proportional to the acceleration and/or a viscous force proportional to the speed is applied by the motor, or when the program provides different reactions in the concentric direction and in the eccentric direction, the computed force to be applied may suffer a discontinuity at the time of the reversal of the direction, which is necessarily prejudicial to the comfort with which the machine is used.

According to one embodiment, the high-level controller 82 implements an algorithm that makes it possible to avoid these discontinuities. To do this, the controller 82 detects a change of direction by the passage of the speed signal through a hysteresis comparator schematically represented in FIG. 11.

On starting the concentric phase, if the speed v>ε, the controller 82 triggers the transition from F2 to F1. This variation is made at a constant rate of variation, for example of the order of 200 N/s.

Similarly, upon the transition from the concentric phase to the eccentric phase, when the speed becomes negative and passes below a threshold v<−ε, the controller 82 triggers the transition from F1 to F2. The threshold value ε is chosen in such a way as to ensure a sufficient stability, namely that the motor does not switch from F1 to F2 in an untimely manner when the athlete decides to make a stop in his or her movement.

In FIG. 11, it is noted that the curves of variation of the force as a function of the speed between the values F1 and F2 are not imposed by the system and in fact depend on the behavior of the user, namely how he or she varies the speed as a function of time, since the system imposes a force variation rate as a function of time.

In addition, the control program may prohibit the motor from performing more than two consecutive changes if the difference in position of the moving part between the two changes does not exceed a certain limit, for example 10 cm.

In other embodiments, the exercise program may also comprise a contribution of elastic force F_e defined as a function of a coefficient of proportionality k₃ and as a function of the position z of the carriage 63:

F _e =k ₃×(z−z0)  (12)

in which z0 is a parameterizable reference height and the position z is determined by the low-level controller 81.

It will therefore be understood that numerous exercise programs can be designed by combining, by choice, additive contributions chosen from the group comprising a contribution of artificial inertia proportional to the measured acceleration, a contribution of viscous friction proportional to the measured speed, an elastic contribution proportional to the measured position and a predetermined load contribution. According to one embodiment, the human-machine interface enables the user to independently set the parameters of each of these contributions, notably the coefficients k, k₂ and k₃.

Although the embodiments described above comprise rotary motors, the control methods described above may be employed with any other type of electric actuator. In particular, a linear motor may be used to generate a force on the manipulation element.

Moreover, the computation of the control signal may be performed in different ways, in a unitary or distributed manner, by means of hardware and/or software components. Hardware components that can be used are custom integrated circuits ASIC, programmable logic arrays FPGA or microprocessors. Software components can be written in different programming languages, for example C, C++, Java or VHDL. This list is not exhaustive.

Although the invention has been described in conjunction with a number of particular embodiments, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described and their combinations provided the latter fall within the framework of the invention.

The use of the verb “comprise” or “include” and its conjugated forms does not preclude the presence of elements or steps other than those stated in a claim. The use of the indefinite article “a” or “an” for an element or a step does not preclude, unless otherwise stipulated, the presence of a plurality of such elements or steps. A number of means or modules may be represented by one and the same hardware element.

In the claims, any reference symbol between brackets would not be interpreted as a limitation on the claim.

Claims

1. An exercise device comprising: a load element (6, 69) intended to be displaced by the force of a user,an electric actuator (1, 76) comprising a moving part (2), the load element (6, 69) being linked to the moving part and the load element being able to displace the moving part,a computer (12, 80) suitable for computing a force to be exerted by the electric actuator and for generating a control signal for the electric actuator as a function of the computed force to be exerted, in such a way that the force exerted by the electric actuator (1) in response to the control signal corresponds to the computed force to be exerted andan acceleration sensor coupled to the moving part (2) for measuring the acceleration of the moving part and for transmitting the measured acceleration to the computer (12, 80),the electric actuator being able to exert a force on the load element (6, 69) via the moving part in response to the control signal,in which the computer (12, 80) is able to compute the force to be exerted as a function of the acceleration measured by the acceleration sensor,characterized in that the device also comprises: a memory of the computer in which is stored a coefficient of proportionality between the measured acceleration and an additive contribution of artificial inertia, anda human-machine interface (86) enabling a user to set the coefficient of proportionality,the computer being able to compute the additive contribution of artificial inertia as a function of the measured acceleration and of the coefficient of proportionality, the force to be exerted computed by the computer as a function of the measured acceleration including the additive contribution of artificial inertia proportional to the measured acceleration obtained by the computer as the result of a multiplication of the measured acceleration by the coefficient of proportionality stored in the memory, in such a way that the force exerted by the electric actuator (1, 76) in response to the control signal includes the additive_contribution of artificial inertia proportional to the acceleration measured by the acceleration sensor and to the coefficient of proportionality stored in the memory.

2. The exercise device as claimed in claim 1, characterized in that the computer (12, 80) is able to vary the coefficient of proportionality as a function of at least one parameter chosen from the position, the speed and the acceleration of the moving part.

3. The exercise device as claimed in claim 1, characterized in that the computer (12, 80) is able to compute the force to be exerted in such a way that the force to be exerted by the electric actuator (1, 76) includes an additive contribution of additional load exhibiting a predetermined direction.

4. The exercise device as claimed in claim 3, characterized in that the computer (12, 80) is able to compute the force to be exerted in such a way that the additive contribution of artificial inertia is oriented in the same direction as the contribution of predetermined direction when the measured acceleration is in the direction opposite the contribution of predetermined direction.

5. The exercise device as claimed in claim 4, characterized in that the computer (12, 80) is able to compute the force to be exerted in such a way as to cancel the additive contribution of artificial inertia when the measured acceleration is in the same direction as the contribution of predetermined direction of the electric actuator (1, 76).

6. The exercise device as claimed in claim 1, characterized in that the link between the load element (6, 69) and the moving part includes a speed reducer for gearing down the force of the motor.

7. The exercise device as claimed in claim 1, characterized in that it comprises a speed sensor suitable for measuring the speed of the moving part (2) and that the computer (12, 80) is able to generate the control signal in such an/ay that the force exerted by the electric actuator (1, 76) includes an additive contribution of viscous friction substantially proportional to the speed measured by the speed sensor.

8. The exercise device as claimed in claim 1, characterized in that the electric actuator (1, 76) is a linear motor or a rotary motor.

9. The exercise device as claimed in claim 1, characterized in that the acceleration sensor comprises: a position coder (10, 84) coupled to the moving part (2) for measuring the position of the moving part, the position coder (10, 84) generating a position signal, andshunt elements (13, 14) suitable for shunting the position signal to determine the acceleration of the moving part (2).

10. The exercise device as claimed in claim 1, characterized in that the exercise device is selected from the group comprising rowing machines, exercise bicycles, lifting bars and guided load appliances.

11. (canceled)

12. The exercise device as claimed in claim 11, characterized in that the computer (12, 80) is able to compute the force to be exerted in such a way that the force to be exerted by the electric actuator (1, 76) includes an additive contribution of additional load exhibiting a predetermined direction, the human-machine interface (86) enabling a user to out the additive contribution of additional load independently of the coefficient of proportionality.

13. The exercise device as claimed in claim 11, characterized in that the human-machine interface (86) enables a user to set the additive contribution of additional load to a zero value.

14. The exercise device as claimed in claim 1, characterized in that the load element (69, 63) can be displaced in a vertical direction and that the computer (12, 80) is able to compute the force to be exerted in the absence of force exerted by the user, in such a way that the force to be exerted by the electric actuator (1, 76) includes a default additive contribution of load compensating a specific weight of the load element (69, 63) without causing any spontaneous displacement of the load clement (69, 63) in the absence of a force exerted by the user,

15. A method for controlling an exercise device comprising: measuring the acceleration of a moving part (2) of an electric actuator in response to the force of a user exerted on a load element (6, 69) linked to the moving part,computing a force to be exerted by the electric actuator as a function of the measured acceleration andgenerating a control signal for controlling the electric actuator (1, 76) with the control signal in such away that the force exerted by the electric actuator (1, 76) in response to the control signal corresponds to the computed force to be exerted, characterized by the steps of:providing a human-machine interface (86) enabling a use o at a coefficient of proportionality between the measured acceleration and an additive contribution of artificial inertia,storing the coefficient of proportionality in a memory,multiplying the measured acceleration by the coefficient of proportionality to obtain the additive contribution of artificial inertia, andobtaining the force to be exerted computed as a function of the measured acceleration including the additive contribution of artificial inertia proportional to the measured acceleration, in such a way that the force exerted by the electric actuator (1, 76) on the load element (6, 69) via the moving part (2) in response to the control signal includes an additive contribution of artificial inertia proportional to the measured acceleration.