Patent Application
20240405713
The present invention relates to a control technique of a machine, and particularly relates to a control device, a machine system, and a display device having a function of dealing with a change in viscous friction.
A technique for stopping motion of a machine by issuing an excessive error alarm when a position error being a deviation between a command movement amount and an actual movement amount of a servomotor is equal to or more than a prescribed value, has been proposed (for example, PTL 1). However, when a machine is left standing in a low-temperature environment for a fixed period of time, kinematic viscosity of a lubricant that lubricates an actuator of the machine increases. Thus, when the cooled machine starts motion, a motion command exceeding capacity of the servomotor may be input in response to an increase in a viscous frictional force generated in the actuator, a deviation between a command position and an actual position may increase, a position error may exceed a prescribed value, and an excessive error alarm may be issued. In this case, an abnormality is determined, and motion of the machine is stopped, which also leads to a stopping of the entire system including the machine, and results in an adverse influence on production, operation, and the like.
On the other hand, when the machine is in a high-temperature environment, kinematic viscosity of the lubricant decreases, and a viscous frictional force generated in the actuator decreases. Thus, a position error does not exceed the prescribed value, and the error increasing alarm is not issued. However, in the high-temperature environment, there is a possibility that a motion limitation on a speed, acceleration, and the like of the servomotor at a reference temperature (for example, a normal temperature) can be slightly relaxed within a range that capacity of the actuator is not exceeded. As the background art related to the present application, the following literature is publicly known.
In order to solve a problem that it takes considerable time to detect an abnormality at a low rotation speed of a motor when a threshold value of a position error at a maximum rotation speed of the motor is set, PTL 1 describes the following. A simulation of a servo control system approximated by a first order transmission function by using, as a time constant, a reciprocal of a position gain of the servo control system is performed simultaneously with driving control of a servomotor, and an excessive error alarm is issued when a position error acquired from the simulation and an actual position error acquired from the servo control are equal to or more than a predetermined value.
When a robot is operated in a low-temperature environment, grease (lubricant) used for a mechanism unit including a motor and a reduction gear becomes hard, and friction increases further than that in a normal-temperature environment. Thus, an estimated disturbance value exceeds a threshold value regardless of no occurrence of a collision in reality, and the collision is detected by mistake. Accordingly, PTL 2 describes that whether a driving axis of a robot is in a low-temperature environment is determined in a control device of the robot, and a threshold value is corrected upward from a value for the normal-temperature environment when the driving axis is determined to be in the low-temperature environment.
PTL 3 describes a servo control device. The servo control device has purposes of more accurately determining a frictional force that changes with time and temperature, switching a frictional coefficient dynamically with respect to a time change and a temperature change without depending on a change in time and temperature, and always maintaining control performance of position control and flexible control high. The servo control device performs a simulation on position control and speed control, compares an output of a speed controller and an output of a simulation speed controller, generates a friction model from the output of a comparison unit, and performs compensation based on an output of the friction model.
In order to solve the following problems, PTL 4 describes a robot control device that controls a detection means for detecting a collision of a robot in such a way that the collision of the robot is less likely to be detected when a predetermined condition indicating that a temperature of the robot is low is satisfied. The problems include a problem that a collision cannot be detected due to a change in a threshold value in spite of the fact that a temperature of a robot is not low and friction is not great when adopting a configuration for changing a threshold value of a disturbance value by determining whether an elapsed time since motor power is turned on exceeds a prescribed value, and a problem that a collision cannot be detected due to a failure to determine whether an estimated value of a frictional coefficient converges by a frictional change in a region where a temperature of a robot is low when adopting a configuration for changing a threshold value of a disturbance value by determining whether a change amount of an estimated value of a frictional coefficient is equal to or less than a prescribed value.
PTL 5 describes a motor control device having purposes of appropriately estimating a frictional force acting on an output shaft of a motor and compensating for disturbance by a frictional force without requiring highly precise modeling of a frictional characteristic and highly precise identification of a related physical quantity. The motor control device includes a disturbance observer device that receives, as a control input, a current command value to a motor, a rotation speed of the motor, and a measurement value of torsion torque of an output shaft connected to the motor via a speed reduction mechanism, and suppresses disturbance by frictional torque acting on the output shaft of the motor. The disturbance observer device calculates a torque compensation value for compensating for frictional torque, based on the control input, and a sensitivity function indicating a characteristic of compensation value calculation is set based on the rotation speed of the motor.
An object of the present invention is, in view of the conventional problems, to provide a control technique of a machine that deals with a change in viscous friction.
One aspect of the present disclosure provides a control device including: a temperature acquisition unit configured to acquire a detected temperature; a frictional force calculation unit configured to calculate a viscous frictional force generated in an actuator of a machine at the detected temperature and a reference temperature; and a control unit configured to impose a motion limitation on the machine, based on the viscous frictional force, in such a way that capacity of the actuator is not exceeded.
Another aspect of the present disclosure provides a machine system including: a machine; a temperature sensor; a temperature acquisition unit configured to acquire a detected temperature from the temperature sensor; a frictional force calculation unit configured to calculate a viscous frictional force generated in an actuator of the machine at the detected temperature and a reference temperature; and a control unit configured to impose a motion limitation on the machine, based on the viscous frictional force, in such a way that capacity of the actuator is not exceeded.
A different aspect of the present disclosure provides a display device including a display unit that emphasizes and displays a motion command of an actuator or a machine on which a motion limitation is imposed when a state is determined to be a temperature state where the motion limitation is to be imposed on the machine.
According to the one aspect and the other aspect of the present disclosure, even when a viscous frictional force increases due to a low-temperature environment, a motion limitation on a machine is tightened in such a way that capacity of an actuator is not exceeded. Accordingly, occurrence of an excessive error alarm of a position error can be prevented, and thus the machine can continue motion. On the other hand, when a viscous frictional force decreases due to a high-temperature environment, a motion limitation on the machine is relaxed in such a way that capacity of the actuator is not exceeded. Accordingly, the machine can perform motion relatively rapidly.
In the present disclosure, a term “imposing a motion limitation” includes not only a case where a motion limitation on a machine is tightened when a viscous frictional force increases due to a low-temperature environment, but also a case where a motion limitation on a machine is relaxed when a viscous frictional force decreases due to a high-temperature environment.
According to the different aspect of the present disclosure, when a state is determined to be a temperature state where a motion limitation is to be imposed on a machine, a motion command of an actuator or the machine on which the motion limitation is imposed is emphasized and displayed on the display unit, and thus a user can visually recognize the motion command of the actuator or the machine on which the limitation is imposed, and can easily recognize that the machine is not performing motion as intended.
Hereinafter, embodiments according to the present disclosure will be described in detail with reference to accompanying drawings. The same or similar element is denoted by the same or similar reference sign in each of the drawings. Further, the embodiments described below do not limit a technical scope of the invention described in claims and meaning of a term. It should be noted that, in the present specification, a term “low temperature” means a temperature (for example, lower than 10° C.) lower than a reference temperature (for example, 25° C.), and a term “high temperature” means a temperature (for example, higher than 40° C.) higher than the reference temperature. Further, it should be noted that, in the present specification, a term “frictional force” includes not only a frictional force in a narrow sense but also frictional torque.
Hereinafter, one example of a configuration of a machine system 1 according to one embodiment will be described in detail.
The machine 10 is formed of a multijoint robot, which is not limited thereto. In another embodiment, the machine 10 may be formed of another industrial robot (robot arm) such as a single joint robot, a dual arm robot, and a parallel link robot. Alternatively, in a different embodiment, the machine 10 may be formed of a robot in another manner such as a humanoid, instead of an industrial robot. Alternatively, in a still different embodiment, the machine 10 may also be formed of another industrial machine such as a construction machine and an agricultural machine or another machine such as a vehicle and an aircraft, instead of a robot.
The machine 10 includes a base 11, and a revolving barrel 12 supported rotatably about a first axis line J1 with respect to the base 11. Further, the machine 10 includes a first arm 13 supported rotatably about a second axis line J2 orthogonal to the first axis line J1 with respect to the revolving barrel 12, a second arm 14 supported rotatably about a third axis line J3 parallel to the second axis line J2 with respect to the first arm 13, and a three-axis wrist unit 15 attached to a tip of the second arm 14. Furthermore, the machine 10 may include a tool 16 that can be attached to a tip of the wrist unit 15. The tool 16 includes, for example, a hand, a cutting tool, a fastening tool, a welding tool, a sealing tool, and the like.
In this way, the machine 10 includes a plurality of relatively movable links such as the revolving barrel 12, the first arm 13, the second arm 14, and the wrist unit 15. Since the machine 10 according to the present embodiment is a multiaxial machine, the machine 10 includes a plurality of actuators 17 (see
Further, the actuator 17 is formed of a rotary actuator including a rotary motor, which is not limited thereto. In another embodiment, the actuator 17 may be formed of a linear actuator including a linear motor. Mechanical elements such as a shaft, a bearing, and a gear of the actuator 17 are lubricated by a lubricant (not illustrated) such as grease and lubricating oil. Since a lubricant has kinematic viscosity changing in accordance with temperature, a viscous frictional force generated in the actuator 17 also changes.
Thus, the machine system 1 further includes a temperature sensor 18. The temperature sensor 18 is formed of a thermocouple, a thermistor, a resistance temperature detector, or the like. The temperature sensor 18 is an existing temperature sensor mounted on the actuator 17 (for example, an electric motor), which is not limited thereto. In another embodiment, the temperature sensor 18 may be a temperature sensor mounted inside a lubricating room that lubricates the actuator 17 (for example, a reduction gear and a bearing), a temperature sensor mounted inside or outside the machine 10, a temperature sensor mounted on the control device 20 or the teaching device 30, or a temperature sensor disposed near the control device 20 or the teaching device 30. The existing temperature sensor 18 detects a temperature of the actuator 17 (for example, a coil, a stator core, a bearing, and the like of an electric motor), whereas the other temperature sensor 18 detects a temperature of a lubricant inside a lubricating room and detects an ambient temperature (fluid temperature around the machine 10) inside or outside the machine 10. An ambient temperature outside the machine 10 is a so-called environmental temperature.
The control device 20 is formed of a publicly known programmable logic controller (PLC), which is not limited thereto. In another embodiment, the control device 20 may be formed of another computer device. Although it is not illustrated, the control device 20 includes a processor, a memory, an input/output interface, a timer, and the like (not illustrated) that are connected to one another with a bus. The processor includes a central processing unit (CPU), a micro processing unit (MPU), and the like. The memory includes a random access memory (RAM), a read only memory (ROM), and the like. The input/output interface includes an A/D converter, a D/A converter, and the like.
As illustrated in
With reference to
As illustrated in
As illustrated in
In the machine system 1 configured as described above, when the machine 10 is left standing in a low-temperature environment for a fixed period of time, kinematic viscosity of a lubricant that lubricates the actuator 17 of the machine 10 increases. Thus, when the cooled machine 10 starts motion, the motion command 36 exceeding capacity of the actuator 17 may be input in response to an increase in a viscous frictional force generated in the actuator 17, a deviation between a command position and an actual position may increase, a position error may exceed a prescribed value, and an excessive error alarm may be issued. Therefore, the control device 20 has a function of dealing with a change in a viscous frictional force. In a low-temperature environment, the control device 20 tightens a motion limitation on a speed, acceleration, and the like of the actuator 17 or the machine 10, and performs control in such a way as to start motion of the machine 10 relatively slowly.
On the other hand, when the machine 10 is in a high-temperature environment, kinematic viscosity of the lubricant decreases, and a viscous frictional force generated in the actuator 17 decreases. Thus, a position error does not exceed the prescribed value, and no error increasing alarm is issued. However, in the high-temperature environment, the control device 20 relaxes a motion limitation on a speed, acceleration, and the like of the actuator 17 or the machine 10 at a reference temperature, and performs control in such a way as to execute motion of the machine 10 relatively rapidly.
As illustrated in
Further, the control device 20 may include a storage unit 25 that stores various pieces of information. The storage unit 25 is formed of a memory such as a RAM and a ROM. The storage unit 25 stores a threshold value of a detected temperature, a threshold value of a stop time before operation of the machine 10, a threshold value of an operating time after operation of the machine 10, a viscous frictional force estimation equation, and the like.
It should be noted that a component other than the storage unit 25 of the control device 20 is formed of a part or the whole of a computer program, which is not limited thereto. In another embodiment, the component may be formed of a part or the whole of an electric circuit, a semiconductor integrated circuit, or the like. Further, in another embodiment, an element other than the control unit 28 may be disposed in a host computer device that can be connected to the control device 20 in a wired or wireless manner.
The temperature acquisition unit 21 acquires a detected temperature by multiplying, by a temperature coefficient, an output value (for example, a voltage value and the like) of the temperature sensor 18 subjected to A/D conversion, and converting the output value to a temperature of the actuator 17 (for example, a coil, a stator core, and the like of an electric motor). In other words, even when the temperature sensor 18 outputs a temperature of a lubricant or an ambient temperature inside or outside the machine 10, the temperature acquisition unit 21 acquires a temperature of the actuator 17. A temperature coefficient that converts an output value of the temperature sensor 18 to a temperature of the actuator 17 may be stored in the storage unit 25 or defined in a program.
The frictional force calculation unit 27 calculates each of a viscous frictional force τd generated in the actuator 17 at a detected temperature and a viscous frictional force τr generated in the actuator 17 at a reference temperature. In this way, the control unit 28 can impose a motion limitation on the machine 10, based on a change amount Δτ (=τd−τr) of the viscous frictional force between the detected temperature and the reference temperature. The viscous frictional force τ is obtained from the following viscous frictional force estimation equation, for example.
In the viscous frictional force estimation equation (Equation 1), μ is a viscous frictional coefficient, v is kinematic viscosity of a lubricant, s is a speed (for example, a rotation speed) of the actuator 17, and n is an exponent of a constant. The kinematic viscosity v in Equation 1 is obtained from the following kinematic viscosity estimation equation, based on the publicly known Andrade's viscosity calculation equation and a definition of kinematic viscosity.
In the kinematic viscosity estimation equation (Equation 2), f and e are constants, and T is a temperature (for example, an absolute temperature) of a lubricant. As described above, the temperature acquisition unit 21 acquires a detected temperature of the actuator 17 (for example, a coil, a stator core, a bearing, and the like of an electric motor), and thus the frictional force calculation unit 27 estimates a temperature T of the lubricant, based on the detected temperature of the actuator 17. The constants f and e are predetermined based on data such as a temperature, viscosity, and a density of the lubricant used for the actuator 17. The constants f and e may be stored in the storage unit 25 or defined in a program.
Further, the viscous frictional coefficient μ in the viscous frictional force estimation equation (Equation 1) is predetermined by causing the machine 10 to perform standard motion in various temperature environments (such as a low-temperature environment, a reference temperature, and a high-temperature environment), and performing, in advance, an experiment that identifies the viscous frictional coefficient μ from Equation 1, based on a command value (such as a speed command value and a torque command value), a detection value (such as a speed detection value and a torque detection value), a temperature, and the like of the actuator 17. The viscous frictional coefficient μ may be stored in the storage unit 25 as a database in association with various temperatures or defined in a program.
Alternatively, as illustrated in
Alternatively, the frictional force calculation unit 27 may perform an experiment that identifies a relationship between a temperature and a viscous frictional force without using the viscous frictional coefficient μ, predetermine a temperature-frictional force database, and calculate each of viscous frictional forces τd and τr at a detected temperature and a reference temperature, based on the temperature-frictional force database. The temperature-frictional force database may be stored in the storage unit 25 or defined in a program.
Further, as the speed s of the actuator 17 in the viscous frictional force estimation equation (Equation 1), a maximum speed smax (for example, a maximum rotation speed) in terms of specifications of the actuator 17 at a reference temperature may be used in such a way that a motion limitation on the machine 10 at a detected temperature is not too tightened. The maximum speed smax of the actuator 17 at the reference temperature may be stored in the storage unit 25 or defined in a program.
The control unit 28 imposes a motion limitation on the machine 10, based on the viscous frictional forces τd and τr at the detected temperature and the reference temperature being calculated as described above, in such a way that capacity of the actuator 17 is not exceeded. The control unit 28 includes an upper limit calculation unit 28a that calculates an upper limit value of motion of the actuator 17 or the machine 10, a command limiting unit 28b that limits the motion command 36 of the actuator 17 or the machine 10, based on the upper limit value, and a driving control unit 28c that controls driving of the actuator 17, based on the motion command 36 on which the motion limitation is imposed.
The upper limit calculation unit 28a calculates an upper limit value of at least one of a speed and acceleration of the actuator 17, based on the change amount Δτ (=τd−τr) of the viscous frictional force between the detected temperature and the reference temperature. An upper limit value slim of the speed of the actuator 17 at the detected temperature is calculated from the following equation, for example.
In Equation 3, τd is a viscous frictional force at the detected temperature, Δτ is a change amount of the viscous frictional force between the detected temperature and the reference temperature, and μd is a viscous frictional coefficient at the detected temperature. In other words, the upper limit calculation unit 28a tightens or relaxes the upper limit value slim of the speed by the change amount Δτ of the viscous frictional force between the detected temperature and the reference temperature.
Meanwhile, an upper limit value alim of the acceleration of the actuator 17 is calculated from the following equation, for example.
In Equation 4, amax is maximum acceleration of the actuator 17, Jm is moment of inertia (for example, rotor inertia), and Δτ is a change amount of the viscous frictional force between the detected temperature and the reference temperature. In other words, the upper limit calculation unit 28a tightens or relaxes the upper limit value alim of the acceleration by the change amount Δτ of the viscous frictional force between the detected temperature and the reference temperature.
The command limiting unit 28b limits at least one of a speed command and an acceleration command (a current command (for example, a torque command)) of the actuator 17 in such a way that at least one of the upper limit value slim of the speed and the upper limit value alim of the acceleration of the actuator 17 is not exceeded. In other words, the command limiting unit 28b limits at least one of the speed command and the acceleration command of the actuator 17 in the motion program 35.
Alternatively, in another embodiment, the command limiting unit 28b may limit at least one of a speed command and an acceleration command of the machine 10 in such a way that respective upper limit values slim1 to slimn and alim1 to alimn of the speed and the acceleration of n (n is an integer of one or more) actuator 17.
The speed and the acceleration of the machine 10 are a speed and acceleration of a tip (for example, an origin of the tool coordinate system C2) of the machine 10. Further, since the machine 10 includes n actuator 17, the command limiting unit 28b converts, based on forward kinematics, the upper limit values slim1 to slimn and alim1 to alimn of at least one of the speed and the acceleration of each n actuator 17 to upper limit values Slim and Alim of at least one of the speed and the acceleration of the tip of the machine 10.
The upper limit values slim1 to slimn of the speed of each n actuator 17 are expressed by differentiating positions q1 to qn (for example, a rotational angle for a rotary actuator, a linear position for a linear actuator) of the actuator 17 with respect to a time t. On the other hand, the upper limit value Slim of the speed of the tip of the machine 10 is expressed by differentiating a position and a posture (x, y, z, ω, p, r) (for example, a position and a posture of the tool coordinate system C2 in the reference coordinate system C1) of the machine 10 with respect to the time t. Therefore, the upper limit value Slim of the speed of the tip of the machine 10 is obtained from, for example, the following equation by forward kinematics.
In Equation 5, J is a Jacobian matrix, is predetermined according to the machine 10 (such as a length of a link and a movable range of a link), and is stored in the storage unit 25 or defined in a program.
On the other hand, the upper limit value Alim of the acceleration of the tip of the machine 10 may be obtained by differentiating the upper limit value Slim of the speed of the tip of the machine 10 with respect to the time t or obtained from the upper limit values alim1 to alimn of the acceleration of the actuator 17 by forward kinematics.
The command limiting unit 28b limits at least one of the speed command and the acceleration command of the machine 10, based on the upper limit values Slim and Alim of at least one of the speed and the acceleration of the tip of the machine 10. In other words, the command limiting unit 28b limits at least one of the speed command and the acceleration command of the machine 10 in the motion program 35.
As described above, even when a viscous frictional force increases due to a low-temperature environment, the control device 20 tightens a motion limitation on the machine 10 in such a way that capacity of the actuator 17 is not exceeded. Accordingly, occurrence of an excessive error alarm of a position error can be prevented, and thus the machine 10 can continue motion.
On the other hand, when a viscous frictional force decreases due to a high-temperature environment, the control device 20 relaxes a motion limitation on the machine 10 in such a way that capacity of the actuator 17 is not exceeded. Accordingly, the machine 10 can perform motion relatively rapidly.
Further, the command limiting unit 28b sends, to the display unit 32, a display command that emphasizes and displays the motion command 36 of the actuator 17 or the machine 10 on which a motion limitation is imposed. As illustrated in
With reference to
With reference to
Further, the control device 20 may further include a stop time calculation unit 22 that calculates a stop time before operation of the machine 10, an operating time calculation unit 23 that calculates an operating time after operation of the machine 10, and a temperature state determination unit 24 that determines whether a state is a temperature state where a motion limitation is to be imposed on the machine 10, based on at least one of a detected temperature, the stop time, and the operating time.
The stop time calculation unit 22 calculates a stop time before operation of the machine 10 by measuring a time interval since the power is turned off (power OFF) until the power is turned on (power ON) by using a timer function of the control device 20. Alternatively, in another embodiment, the stop time calculation unit 22 may measure a time interval since the power is turned off (power OFF) until a motion start of the machine 10.
The operating time calculation unit 23 calculates an operating time after operation of the machine 10 by measuring a cumulative operating time since the power is turned on (power ON) until a current time by using the timer function of the control device 20. Alternatively, in another embodiment, the operating time calculation unit 23 may roughly calculate an operating time of the machine 10 by simply measuring a time interval since the power is turned on (power ON) until a current time by using the timer function of the control device 20.
The temperature state determination unit 24 determines whether a lubricant is in a low-temperature state to the extent that a motion limitation is to be imposed (tightened) on the machine 10 by determining whether a detected temperature T is lower than a threshold value (for example, 10° C.) and determining whether a stop time before operation of the machine 10 exceeds a threshold value (for example, 9 hours). When a stop time before operation of the machine 10 is short, there is a possibility that the machine 10 is still warm and a viscous frictional force at a detected temperature has not been changed much from a viscous frictional force at a reference temperature. Thus, a temperature state of a lubricant can be accurately determined by considering a stop time before operation of the machine 10.
On the other hand, the temperature state determination unit 24 determines whether a lubricant is in a high-temperature state to the extent that a motion limitation is to be imposed (relaxed) on the machine 10 by determining whether the detected temperature T exceeds a threshold value (for example, 40° C.). The threshold value of the detected temperature T and the threshold value of the stop time described above may be stored in the storage unit 25 or defined in a program.
When the detected temperature T falls outside a threshold value (for example, 10° C.<T<40° C.) (i.e., when a lubricant is determined to be in a low-temperature state or a high-temperature state), the temperature state determination unit 24 sends a frictional coefficient calculation command to the frictional coefficient calculation unit 26 or sends a frictional force calculation command to the frictional force calculation unit 27.
As described above, the frictional coefficient calculation unit 26 calculates each of the viscous frictional coefficients μd and μr at a detected temperature and a reference temperature, and sends the calculated viscous frictional coefficients μd and μr to the frictional force calculation unit 27. As described above, the frictional force calculation unit 27 calculates each of the viscous frictional forces τd and τr at the detected temperature and the reference temperature, and sends the calculated viscous frictional forces τd and τr to the control unit 28. As described above, the control unit 28 imposes a motion limitation on the machine 10, based on the change amount Δτ of the viscous frictional force between the detected temperature and the reference temperature, in such a way that capacity of the actuator 17 is not exceeded.
Further, when the temperature state determination unit 24 determines that a lubricant is in a low-temperature state and determines that an operating time after operation of the machine 10 exceeds a threshold value (for example, 10 minutes), the lubricant is already warm, and thus the temperature state determination unit 24 may send a reset command for a motion limitation (tightening) of the machine 10 to the command limiting unit 28b, and the command limiting unit 28b may reset the motion limitation (tightening) of the machine 10, based on the reset command. Alternatively, in another embodiment, when the temperature state determination unit 24 determines that a lubricant is in a low-temperature environment, and determines that an operating time after operation of the machine 10 exceeds a threshold value (for example, 10 minutes) and the detected temperature T at that time exceeds a threshold value (for example, 10° C.), the temperature state determination unit 24 may send the reset command for the motion limitation (tightening) of the machine 10 to the command limiting unit 28b. In this way, a temperature state of a lubricant can be more accurately determined.
On the other hand, when the temperature state determination unit 24 determines that a lubricant is in a high-temperature environment and determines that the detected temperature T exceeds a maximum allowable threshold value (for example, 90° C.), the temperature state determination unit 24 sends a reset command for a motion limitation (relaxation) of the machine 10 to the command limiting unit 28b. The maximum allowable threshold value of the detected temperature T means a maximum allowable temperature in terms of specifications of the actuator 17 (for example, an electric motor). For example, when the actuator 17 exceeds a maximum allowable temperature of 90° C., the actuator 17 is to be overheated, and thus relaxation of a motion limitation on the machine 10 needs to be reset.
Further, when the temperature state determination unit 24 determines that a lubricant is in a temperature state to the extent that a motion limitation is to be imposed on the machine 10, the temperature state determination unit 24 may send, to the display unit 32, a display command that displays a warning message 34 indicating that the lubricant is in a low-temperature state or a high-temperature state. In the example in
With reference to
In this way, a user can simulate a motion limitation on the machine 10 due to a viscous frictional force at an input designated temperature. In other words, when a designated temperature is a low temperature, a motion speed and a motion execution time in a state where a motion limitation on the machine 10 is tightened can be simulated. Meanwhile, when a designated temperature is a high temperature, a motion speed and a motion execution time in a state where a motion limitation on the machine 10 is relaxed can be simulated.
Hereinafter, one example of motion of the machine system 1 according to the present embodiment will be described in detail.
In step S3, the temperature state determination unit 24 determines whether a lubricant is in a low-temperature state to the extent that a motion limitation is to be imposed (tightened) on the machine 10 by determining whether the detected temperature T is lower than a threshold value (for example, 10° C.) and determining whether a stop time before operation of the machine 10 exceeds a threshold value (for example, 9 hours). When the temperature state determination unit 24 determines that the detected temperature T is equal to or higher than the threshold value (for example, 10° C.) or the stop time does not exceed the threshold value (for example, 9 hours) (NO in step S3), in step S4, the command limiting unit 28b resets a limitation (tightening) on a motion command of the actuator 17 or the machine 10 that has already been performed, and ends a function of dealing with a change in viscous friction.
On the other hand, when the temperature state determination unit 24 determines that the detected temperature T is lower than the threshold value (for example, 10° C.) and the stop time exceeds the threshold value (for example, 9 hours) (YES in step S3), the warning message 34 warning that the lubricant is in the low-temperature state where the motion limitation on the machine 10 is to be tightened may be displayed on the display unit 32.
Further, in order to impose (tighten) the motion limitation on the machine 10, in step S5, the frictional force calculation unit 27 calculates each of the viscous frictional forces τd and τr at the detected temperature and a reference temperature, based on the viscous frictional force estimation equation (Equation 1). It should be noted that a viscous frictional coefficient is stored in the storage unit 25 or a storage unit of an external device by performing an experiment in advance, or the frictional coefficient calculation unit 26 calculates each of the viscous frictional coefficients μd and μr at the detected temperature and the reference temperature. Alternatively, the frictional force calculation unit 27 may calculate each of the viscous frictional forces μd and μr at the detected temperature and the reference temperature, based on a temperature-frictional force database, without using the viscous frictional coefficients μd and μr.
In step S6, the upper limit calculation unit 28a calculates the upper limit values slim1 to slimn and alim1 to alimn of motion of the actuator 17 or the upper limit values Slim and Alim of motion of the machine 10, based on the viscous frictional forces τd and τr at the detected temperature and the reference temperature, in such a way that capacity of the actuator 17 is not exceeded. In step S7, the command limiting unit 28b imposes (tightens) a limitation on the motion command 36 of the actuator 17 or the machine 10, based on the upper limit value.
Further, in step S8, the command limiting unit 28b may emphasize and display, on the display unit 32, the motion command 36 on which the motion limitation is imposed (tightened). Furthermore, the command limiting unit 28b may display, on the display unit 32, the upper limit values slim1 to slimn and alim1 to alimn or Slim and Alim of motion near the motion command 36 on which the motion limitation is imposed.
In the low-temperature state where the motion limitation on the machine 10 is tightened, in step S9, the temperature state determination unit 24 determines whether an operating time of the machine 10 has exceeded a threshold value (for example, 10 minutes). When the temperature state determination unit 24 determines that the operating time of the machine 10 has not exceeded the threshold value (for example, 10 minutes) (NO in step S9), the temperature state determination unit 24 determines that a lubricant is still in the low-temperature state, and repeats the determination in step S9 until the operating time exceeds the threshold value (for example, 10 minutes).
On the other hand, when the temperature state determination unit 24 determines that the operating time of the machine 10 has exceeded the threshold value (for example, 10 minutes) in the low-temperature state where the motion limitation on the machine 10 is tightened (YES in step S9), the temperature state determination unit 24 determines that the lubricant has gone through the low-temperature state, and, in step S4, the command limiting unit 28b resets the limitation (tightening) on the motion command of the actuator 17 or the machine 10, and ends a function of dealing with a change in viscous friction.
In step S3a, the temperature state determination unit 24 determines whether a lubricant is in a high-temperature state to the extent that a motion limitation is to be imposed (relaxed) on the machine 10 by determining whether the detected temperature T is equal to or higher than a threshold value (for example, 40° C.). When the temperature state determination unit 24 determines that the detected temperature T is lower than the threshold value (for example, 40° C.) (NO in step S3a), in step S4, the command limiting unit 28b resets a limitation (tightening) on a motion command of the actuator 17 or the machine 10 that has already been performed, and ends a function of dealing with a change in viscous friction.
On the other hand, when the temperature state determination unit 24 determines that the detected temperature T is equal to or higher than the threshold value (for example, 40° C.) (YES in step S3a), the warning message 34 warning that the lubricant is in the high-temperature state where the motion limitation on the machine 10 is relaxed may be displayed on the display unit 32.
Further, in order to impose (relax) the motion limitation on the machine 10, in step S5, the frictional force calculation unit 27 calculates each of the viscous frictional forces τd and τr at the detected temperature and a reference temperature, based on the viscous frictional force estimation equation (Equation 1). It should be noted that a viscous frictional coefficient is stored in the storage unit 25 or a storage unit of an external device by performing an experiment in advance, or the frictional coefficient calculation unit 26 calculates each of the viscous frictional coefficients μd and μr at the detected temperature and the reference temperature. Alternatively, the frictional force calculation unit 27 may calculate each of the viscous frictional forces τd and τr at the detected temperature and the reference temperature, based on a temperature-frictional force database, without using the viscous frictional coefficients μd and μr.
In step S6, the upper limit calculation unit 28a calculates the upper limit values slim1 to slimn and alim1 to alimn of motion of the actuator 17 or the upper limit values Slim and Alim of motion of the machine 10, based on the viscous frictional forces τd and τr at the detected temperature and the reference temperature, in such a way that capacity of the actuator 17 is not exceeded. In step S7, the command limiting unit 28b imposes (relaxes) a limitation on the motion command 36 of the actuator 17 or the machine 10, based on the upper limit value.
Further, in step S8, the command limiting unit 28b may emphasize and display, on the display unit 32, the motion command 36 on which the motion limitation is imposed (relaxed). Furthermore, the command limiting unit 28b may display, on the display unit 32, the upper limit values slim1 to slimn and alim1 to alimn or Slim and Alim of motion near the motion command 36 on which the motion limitation is imposed.
In the high-temperature state where the motion limitation on the machine 10 is relaxed, in step S9a, the temperature state determination unit 24 determines whether the detected temperature T is equal to or higher than a maximum allowable threshold value (for example, 90° C.) in order to prevent overheating of the actuator 17. When the temperature state determination unit 24 determines that the detected temperature T is lower than the maximum allowable threshold value (for example, 90° C.) (NO in step S9a), the temperature state determination unit 24 determines that the detected temperature T is in a state where there is room for the maximum allowable temperature in terms of specifications of the actuator 17, and repeats the determination in step S9a until the detected temperature T is equal to or higher than the maximum allowable threshold value (for example, 90° C.).
On the other hand, when the temperature state determination unit 24 determines that the detected temperature T is equal to or higher than the maximum allowable threshold value (for example, 90° C.) in the high-temperature state where the motion limitation on the machine 10 is relaxed (YES in step S9a), the temperature state determination unit 24 determines that the detected temperature T has risen to the vicinity of the maximum allowable temperature in terms of specifications of the actuator 17, and, in step S4, the command limiting unit 28b resets the limitation (relaxation) on the motion command of the actuator 17 or the machine 10, and ends a function of dealing with a change in viscous friction.
As described above, according to the present embodiment, even when a viscous frictional force increases due to a low-temperature environment, a motion limitation on the machine 10 is tightened in such a way that capacity of the actuator 17 is not exceeded. Accordingly, occurrence of an excessive error alarm of a position error can be prevented, and thus the machine 10 can continue motion. On the other hand, when a viscous frictional force decreases due to a high-temperature environment, a motion limitation on the machine 10 is relaxed in such a way that capacity of the actuator 17 is not exceeded. Accordingly, the machine 10 can perform motion relatively rapidly.
Further, when a state is determined to be a temperature state where a motion limitation is to be imposed on the machine 10, a motion command of the actuator 17 or the machine 10 on which the motion limitation is imposed (tightened or relaxed) is emphasized and displayed on the display unit 32, and thus a user can visually recognize the motion command of the actuator 17 or the machine 10 on which the limitation is imposed, and can easily recognize that the machine 10 is not performing motion as intended.
While various embodiments have been described in the present specification, the present invention is not limited to the embodiments described above, and it will be understood that various modifications can be made within the scope of the claims below.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/037217 | 10/7/2021 | WO |
