Patent Application
20240033900
The invention relates to an exoskeleton for supporting a walking or bending movement of a wearer.
Exoskeletons are artificial, mechanical support structures attached to a wearer's body from the outside to relieve or support the wearer's body muscles. As active exoskeletons, i.e. exoskeletons with active, mostly electromotive actuators, they are used, for example, to support walking or bending movements and thus must transmit or initiate forces or torques between the wearer's limbs and torso.
The actuators 103 can be used to generate an erecting moment between each thigh support structure 104A/B and the upper body connection structure 101, i.e. between a thigh and the upper body of the wearer.
In prior art exoskeletons, thigh support structures are permanently connected to a left or right thigh of the wearer via straps enclosing the thigh. Such straps are cumbersome to put on and uncomfortable for the wearer, as they tend to rub against the skin, hinder free breathing of the skin and can lead to sores.
In order to be able to introduce a supporting torque into the thighs when needed, it must be ensured that thigh support structures are in contact with and rest on the respective thigh at all times. This is naturally achieved when the thigh moves forward (forward in relation to the sagittal plane usually used in anatomy).
When the thigh moves backwards, however, there is no natural contact between the thigh and the thigh support. For readjustment or tracking, a backward directed moment must act on the thigh support structure or the associated actuator from the outside.
In the state of the art, this is realised e.g. via elastic tension straps which run posteriorly between a hip frame and leg straps of thigh support structures. The wearer must therefore apply additional force against the tension straps during a forward movement of the thigh. Another disadvantage of tension straps is that they can easily get caught or be accidentally caught by passing vehicles such as forklift trucks. Therefore, at least in some areas of application, exoskeletons with tension straps cannot be used for safety reasons.
It is also known from the prior art to ensure the continuous contact of the thigh attachments to the thigh in a torque-controlled manner: In this case, a control unit of the exoskeleton always controls an actuator so that at least a minimal torque is applied to the thighs. In this case, too, the wearer must always work against this torque when moving the thigh forward. Such a control of the actuators is disadvantageous, on the one hand because the wearer always has to apply an additional force to overcome the torque applied via the actuator in order to move a thigh, and on the other hand because the generation of a torque via the exoskeleton's actuator consumes energy and shortens a period of use of the exoskeleton.
Against this background, an objective is to provide an exoskeleton that overcomes at least some disadvantages of the prior art.
The method according to the invention is based on the idea of replacing a torque-controlled control of the exoskeleton by a distance-based control at least in the case of an idle state (hereinafter referred to as the first operating mode) of the exoskeleton, in which an attachment structure, e.g. a thigh attachment structure (thigh support structure), does not touch the body limb assigned to the attachment structure, e.g. a thigh. Idle state means a state in which the wearer of the exoskeleton does not wish to be actively supported by the exoskeleton and therefore no active forces are to be transmitted to the wearer. Such a state may be, for example, walking.
The method according to the invention provides for controlling an actuator of a channel-and-support structure of an exoskeleton in a selective manner via a control unit. In this case, the channel-and-support structure has an attachment structure for supporting an extremity of a wearer associated with said attachment structure, for example a finger limb, a limb of the leg and/or an arm limb. The attachment structure is designed for direct contact with the limb, for example in the form of a half shell, and is in direct force flow with the actuator via the channel-and-support structure. A distance sensor is arranged in the attachment structure for measuring the distance between the attachment structure and the limb assigned to it, wherein the control unit controls the actuator in a first operating mode in such a way that the attachment structure is held at a predefined distance from the limb. The predefined distance may be, for example, 2 mm, 4 mm or even 6 mm when understanding distance as the shortest distance between the distance sensor and the limb. In other words, the attachment structure does not touch the limb in this first operating mode. The wearer is free to move the limb forward or backward, for example, and the control unit will control the attachment structure to uphold the predefined distance when moving forward or backward. The attachment structure is thus tracking the (moving) limb without contact and in real time while maintaining the predefined distance.
In the first operating mode, also referred to as idle mode, no active forces are applied to the limb via the exoskeleton. This is advantageous for the wearer, as he or she does not have to overcome any counter-torques of the exoskeleton. Furthermore, the attachment structure can be kept at a distance so that skin contact and thus sweating of the wearer is avoided or at least reduced. In contrast to the solutions described above, neither tension straps nor girding of the thigh is necessary. This simplifies the mechanical construction of the attachment structure. It also makes it easier to put on and take off the exoskeleton.
The control unit also controls the actuator in a second operating mode such that the attachment structure abuts upon the limb in a force-conducting, i.e. contacting, manner. In this second operating mode, hereinafter also addressed as “support mode”, a support force can and shall be introduced from the exoskeleton into the limb to support or relieve certain muscle parts of the wearer.
The change between the first and second operating mode takes place depending on at least one variable from the following group:
The erection angle is the angle of the upper body of the wearer with respect to the vertical. Alternatively, it means the technically equivalent upright angle of the exoskeleton's upper body connection structure. The erection angle for a person standing upright is therefore 0°. The inclination angle of an extremity in the anatomical sense means the angle between a major axis of the extremity and the upper body. For the purposes of the present invention, inclination angle means the technically equivalent angle between the channel-and-support structure associated with the limb and a major axis of an attachment structure part to which the channel-and-support structure is connected, minus 180°. The inclination angle thus means the relative angle of the channel-and-support structure with respect to an initial position in which the channel-and-support structure is arranged at an angle of 180° with respect to the upper body connection structure.
Angles are preferably understood to mean the angles in the sagittal plane. Other angular directions are possible.
The method allows switching between the first and second operating modes as needed, with the wearer having full support from the exoskeleton in the second operating mode.
The invention also relates to an exoskeleton:
The exoskeleton comprises an upper body connection structure, a hip frame fixedly connected to the upper body connection structure, and a first or second actuator respectively and preferably laterally attached to the hip frame for supporting a walking or bending movement of a wearer. The upper body connection structure may, for example, be designed as a carrying harness with a rigid back plate.
Furthermore, the first and the second actuator are each assigned a first and a second thigh support structure, respectively, whereby the assignment is made via a first and a second channel-and-support structure, respectively, which extends between the thigh support structure and the actuator or an output shaft or an output flange of the actuator. The first and second channel-and-support structure can be used to transmit forces between a respective thigh support structure and the actuator associated with this thigh support structure. The thigh support structure is preferably designed as a rigid half shell that covers an anterior part of the thigh.
The exoskeleton also comprises at least one control unit (also: controller) for controlling the actuators. A (first or second) distance sensor is arranged in each (first or second) thigh support structure for contactless tracking of the position of a (first or second) thigh of the wearer relative to the (first or second) thigh attachment. The distance sensor measures the distance between the thigh support structure and the thigh in real time so that the control unit can keep the thigh support structure at a predefined distance relative to the thigh even if the thigh is moving.
Such an exoskeleton can increase the wearer's comfort and, in particular, may implement the procedure described above.
Advantageously, one or each distance sensor is a capacitive distance sensor, an optical distance sensor or an ultrasonic distance sensor. Capacitive sensors measure electrical charge changes of a charge carrier due to objects brought close to them, here e.g. a thigh. Capacitive sensors are inexpensive, but due to fluctuating electrical properties on the thigh, they are costly and have to be (re)calibrated regularly. Optical and ultrasonic sensors allow very high resolution accuracies and thus precise distance measurement with smaller fluctuation ranges.
Expediently, each of the distance sensors is arranged in a pocket of the thigh support structure. A pocket is understood to be a rearward recess on a side of the thigh support structure facing the thigh, in which the distance sensor can be ‘burned’. Consequently, the distance sensor does not protrude from the thigh support. In particular, when using a soft thigh pad or a compressible thigh cushion connected to the thigh support structure, the distance between the thigh support structure and the distance sensor can be adjusted so that the thigh pad or thigh cushion rests against the thigh in a non-compressed state. This can give the wearer the feeling of permanent availability of the exoskeleton in an idle state without the user having to overcome counterforces, as the control unit keeps the distance between the thigh support structure and the thigh continuously at the predefined distance even when the thigh is moving.
The control unit of the exoskeleton for controlling the actuators is advantageously set up to perform contactless tracking of the thighs in a first operating mode (idle mode) without supporting a walking movement of the wearer: In this case, the control unit controls the actuators in such a way that each thigh support structure is in each case at a predefined distance unequal to 0 from the thigh assigned to it. This means that there is always a gap between the thigh and the thigh support structure, in which air can circulate, for example. This can give the wearer the feeling of a floating thigh support.
The control unit may be, for example, a microcontroller with a CPU, a data interface for input and output of data signals and a memory comprising instructions stored on the memory for processing incoming data signals.
The control unit is expediently set up to control the actuators in a second operating mode (support mode) to support a bending movement in such a way that, in the second operating mode, each thigh support structure is in contact with its associated thigh in a force-conducting manner. In this state, the wearer can be relieved, especially in the lower back musculature, and be supported when straightening up.
A change between the first and the second operating mode and vice versa can take place under certain permanently or variably defined boundary conditions, in particular if certain variables are present, in particular those determined by sensors of the exoskeleton. Different boundary conditions can be selected for changing from the first to the second operating mode than for changing back from the second operating mode. A certain operating mode of the control unit can also be permanently set on the exoskeleton, for example via a touch-sensitive screen, i.e. such that a change between the operating modes does not take place or only at the request of the wearer.
Advantageously, an erection angle of the upper body connection structure with respect to the vertical in the sagittal plane can be used as a variable for changing the operating mode. For this purpose, the exoskeleton has an inertial unit at the upper body connection structure for detecting the sagittal erection angle. The inertial unit can, for example, be attached to the upper body connection structure, in particular to a rigid back plate of the same. The control unit of the exoskeleton is arranged to remain in the first operating mode and/or to change from the second to the first operating mode as long as or when the erection angle of the upper body connection structure is moving within a predetermined angular range or enters the predetermined angular range. The angular range may expediently be ±20° with respect to the vertical.
Such an angular range corresponds approximately to the angle of the upper body in a standing or walking human. However, the angle range could also be larger, e.g. ±30° or asymmetrical, e.g. ranging between −10° and +20°. By choosing an angle range that is appropriate depending on the application, the first operating mode can be set automatically by the exoskeleton's control unit. This eliminates the need for the wearer to manually switch between the operating modes.
Similarly, it can be advantageous if the control unit is set up to remain in the second operating mode and/or to switch from the first to the second operating mode (support mode) as long as or when the alignment angle of the upper body connection structure moves outside the predefined angle range. This allows the wearer to be actively supported by the exoskeleton, especially in a stooped position.
As alternative or additional criteria for switching between operating modes, the exoskeleton may comprise two angle sensors for detecting a (first and second) inclination angle between the upper body connection structure and each (first and second) channel-and-support structure. The inclination angle can be defined as the angle in the sagittal plane between the upper body connection structure and the channel-and-support structure (or its longitudinal axis). It is to be assumed that the channel-and-support structure has a unique longitudinal axis that approximately corresponds to the longitudinal axis of the thigh. An inclination angle thus corresponds approximately to the bending angle between the hip and the thigh (thigh bone).
In an expedient embodiment, the control unit is set up in such a way that it changes from the first to the second operating mode when both inclination angles of the channel-and-support structures enter a predefined angle range essentially synchronously. In practice, this means that the control unit changes the operating mode when the wearer, for example, squats or bends his upper body in order to lift a load. The angular position of the thighs and thus of the channel-and-supporting structures is usually consistent during such body exercises. By taking the inclination angle into account, an alternative possibility for switching the operating modes is given.
Inclination angle has the meaning of the relative angular deviation between the channel-and-support structure and the upper body connection structure, which deviates from the angular position in which the channel-and-support structure is aligned in straight extension of the upper body connection structure.
However, a change between the operating modes can also be made dependent on the consideration of a plurality of criteria, especially the combination of the inclination angles and the erection angle. If the inclination angles are taken into account in addition to the erection angle of the upper body, a plausibility check (redundancy) can be carried out, for example, and the error rate of an unintentional change of the operating modes can be reduced.
The predefined angular range of the inclination angle can, for example, advantageously be set at less than 45° with respect to an initial position or an initial angle of 180° with respect to the upper body connection structure. The initial position or the initial angle is an angle between the upper body connection structure and the channel-and-support structure of 180°, i.e. in which the channel-and-support structure is aligned in a straight-line with the upper body connection structure.
An inclination angle of −45° (45° in terms of magnitude) corresponds to an absolute inclination angle of the thigh relative to the vertical of 135° for an upright person (erection angle of 0°). This can be a suitable criterion to detect an initial lifting movement of a wearer. Depending on the application, the angle range can also be larger or smaller or individually selected or adapted, i.e. user-specific.
At the same time, the control unit may advantageously be set up to change from the second to the first operating mode when both inclination angles of the channel-and-support structures exit the predefined angular range essentially synchronously, in particular an angular range of more than 20° (i.e. an absolute angle of 160° in the case of an erection angle of 0°). This can be a suitable criterion to determine a completed lifting movement of a wearer.
Furthermore, in a further and advantageous embodiment, the inertial unit of the exoskeleton comprises an acceleration sensor for detecting the acceleration values of the upper body connection structure. The exoskeleton can additionally or alternatively also comprise a (first or second) torque sensor for detecting the torque applied to the (first or second) actuator and/or a (first or second) angular velocity sensor for detecting the angular velocity of the (first or second) actuator. These sensors can be used to further check and increase the plausibility of the conditions for changing the operating modes.
In a particularly advantageous embodiment, the control unit is set up to change from the first to the second operating mode precisely when one of the torque sensors of the first or second actuator measures a torque not equal to 0. In this way, an immediate change of the operating modes can be initiated independently of an angle measurement of the inclination angle and/or erection angle. This case may be occurring, for example, in the case of rapid movements, especially in the case of a wearer falling down.
Advantageous further modifications and further features of the invention are presented in the subclaims and the following description.
The figures show:
To put on an exoskeleton comprising the thigh support structure 8, the wearer only needs to don an upper body connection structure equipped with a carrying harness and to position (“folding inwardly”) the thigh support structure 8 in front of his or her thigh via the passively rotatable second swivel joint 4. An additional attachment via strappings engirding the thigh is not necessary.
The means for attaching a right thigh shown in
The means for attaching a right thigh shown in
In
In
An inertial unit IMU is attached to the upper body connection structure 101 at a suitable location. The inertial unit IMU is equipped with sensor technology for detecting an erection angle α and with sensor technology for detecting the rate of change of the erection angle α. In particular, it may be a gyroscope unit, for example. The erection angle α designates the (absolute) orientation or the angle α with respect to the vertical, see
Furthermore, suitable sensor technology is provided in the actuators 103A/B for detecting the torques applied in the actuators 103A/B, as well as the absolute angular position of the actuators 103A/B and the rate of change of the torques and rates of change of the absolute angular positions. The absolute angular position of the actuators corresponds in each case to an inclination angle β (β1 or β2) of the channel-and-support structures 106A/B relative to the upper body attachment structure.
The inclination angles β are to be understood as the relative deviation of the channel-and-support structures 106A/B from a normal position; the normal position is that in which the upper body connection structure 101 encloses an angle of 180° with a channel-and-support structure 106A/B—in other words a position in which the channel-and-support structures 106A/B are aligned in straight extension of the upper body connection structure 101, as shown in
The exoskeleton 100 of
In
In the first operating mode, the control unit controls the actuators 103A/B in such a way that a predefined distance between each of the thigh support structures 104A/B and the thighs of the wearer associated with them is maintained at any time. The thigh attachments 104A/B therefore always hover in front of the respective (moving) thigh.
This first operating mode is not changed as long as the erection angle α is within a predetermined angular range. This angle range is indicated in
In other words, the control unit detects whether the wearer is in a locomotion mode that can be described as walking and controls the actuators 103A/B in such a way as to maintain a constant distance from the thighs.
In
In
For a better understanding of the control loops of the first and second operating modes shown in
All control variables can also be understood multidimensional, e.g. as a vector with a multitude of individual entries.
For the present case, a control loop according to the invention can be designed according to the illustrations of
In
The control circuit in the first operating mode (idle mode), as shown in
The sensors S2 to S5 are as follows: S2 corresponds to the above-mentioned inertial measurement unit (IMU), which measures the erection angle α of the upper body connection structure 101 as well as the rate of change of the erection angle (r2). S3 represents the measurement sensor for the angular position of the actuator 2, i.e. the inclination angle β of the channel-and-support structure in the form of the angular position of the output flange 3 of the actuator 2 (angle absolute encoder) (r3). S4 represents the distance sensor 10 of the thigh support structure 8 and measures the distance between the thigh support structure 8 and the thigh of the wearer (r4). S5 stands for the Hall sensor necessary for a pulse width modulated control of the actuator M, which measures the angular velocity of one rotor or the rotor of the actuator M (r5).
The controller has a setpoint adjuster, designated as CU2, which processes the measurement signals together with setpoint values into a reference variable w0. The reference variable w0 is the delta between the distance r4 measured via the distance sensor 10 and the setpoint distance c4. A controller control unit CU1 calculates a suitable actuating difference e0 in the form of speed command and direction of rotation command for the actuator on the basis of the reference variable w0 and the measurement signals r2 to r5. The speed command and direction of rotation command e0 is then converted by a motor control unit designated as MCU into a suitable control signal m of an actuator M or of the actuator M connected to the output flange 3. This leads to the movement of the actuator M and thus at the same time to the movement of the channel-and-support structure 5 with the thigh support structure 8. This causes a change in the angular position y0 of the channel-and-support structure 5 and at the same time a change in the (measured) distance r4 of the distance sensor 10 from the thigh of the wearer. The corresponding changes in the measurement signals of the sensors S2 to S5 are fed back into the control loop as the feedback variables r2 to r5, whereby these are also influenced by the movements introduced by the wearer of the exoskeleton (disturbance variable z), in particular forward and backward movements of the thighs.
Suitable conditions are stored in the RAM of the controller at which a change from the first to the second operating mode is to take place. This is indicated by the value c2, which represents a permissible angle range for the erection angle α of the upper body connection structure. The setpoint adjuster CU2 checks for the presence of the conditions and changes the operating mode, if necessary.
In the second operating mode shown in
At the same time, the setpoint adjuster CU2 checks whether conditions for a change to the first operating mode are present or not. In addition to the predefined angular range of the erection angle, this can also be, for example, an asynchronous movement of the channel-and-support structures 5A/B, which can be measured by comparing the inclination angles of both channel-and-support structures 5A/B. This can be used to detect when the wearer begins to walk and active support shall be provided no more.
In contrast to the first operating mode, a torque sensor S1 of the actuator M, which measures the torque applied to the actuator, is necessary in the second operating mode.
The above-described examples of embodiment were described on the basis of the control of exoskeletons for supporting bending and lifting movements, but can of course also be transferred to comparable exoskeletons for supporting other body parts such as the neck, lower leg, upper or lower arms and fingers (with corresponding attachment structures for these body parts). A limitation of the invention idea by the embodiment examples is naturally not intended.
The invention described may provide exoskeletons with automatic switching between a walking mode with a high level of comfort for the wearer and a support mode with active support for the wearer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 112 561.8 | May 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/060816 | 4/25/2022 | WO |
