CN109773792B - Position control device and method for series elastic driver, storage medium and equipment - Google Patents
Position control device and method for series elastic driver, storage medium and equipment Download PDFInfo
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Abstract
The invention provides a position control device and method, storage medium and equipment of a series elastic driver, wherein the device comprises: a sensor for detecting a joint position actual value and an equivalent spring deformation amount of the joint controlled object; the subtracter is used for obtaining a joint position control error according to the joint expected position and the joint position actual value; the PD controller is used for obtaining a PD output value according to the joint position control error; the inverse multiplier is used for obtaining an equivalent spring deflection gain value according to the equivalent spring deflection; the adder is used for obtaining the speed control quantity of the output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value; the multiplier is used for obtaining the speed control quantity of the output shaft of the motor according to the speed control quantity and the reduction ratio of the output shaft of the speed reducer; and the motor controller is used for dragging the joint controlled object to move according to the speed control quantity of the motor output shaft.
Description
Technical Field
The present invention relates to a robot joint position control technology, and in particular, to a robot joint position error compensation method, and more particularly, to a position control apparatus and method, a storage medium, and a device for a Series Elastic Actuator (SEA).
Background
With the rapid development of industrial automation and robot technology, articulated robots such as industrial mechanical arms, bionic foot robots, medical rehabilitation robots and the like play more and more important roles in the fields of industrial medical rehabilitation, space exploration and the like. When the robot performs an operation task, the end position precision of the robot is often ensured by depending on the joint position control of a plurality of joints. From the viewpoint of robot kinematics, it is analyzed that errors in controlling the positions of joints of a robot are accumulated in the end of the robot, and particularly, when the size of a link between the joints is large, a large position error occurs in the end even if the error in controlling the positions of the joints is small, in the case of a tandem end including a plurality of joints (e.g., an end of an industrial robot, a foot end of a bionic-foot robot, a foot end of a humanoid robot, and a hand). Furthermore, joint position control response performance also directly affects tip position response performance: the faster the joint position control response, the faster the tip response; overshoot of the joint position control can further cause large fluctuations in the tip position; the larger the adjustment time of the joint position, the longer the tip position fluctuation time. Therefore, the robot joint position control performance is an important aspect for determining the robot end control performance and is also an important technical basis for the robot to execute operation tasks.
The conventional mechanical arm joint is controlled by Series Elastic Actuators (SEA), which is an Elastic actuator and generally comprises a frame (F), a motor (M), a speed reducer (G), an Elastic element (S) (such as a spring) and a load link (L), and as shown in fig. 1A, 1B and 1C, the SEA generally has three connection modes. The torque control performance of SEA is generally good, and the SEA is often used as a high-precision torque control driver to be applied to a certain joint of a robot and is called as an SEA joint; the SEA joint generally has high flexibility, and the position control error of the SEA joint in position control becomes large due to the load; in a dynamic situation, due to the load inertia, high-precision dynamic tracking is more difficult for the SEA joint; in particular, the high flexibility of the resiliently driven joints makes high precision position control a challenge when the spring rate of the resiliently driven joints is low and the load is high, and so SEA pure joint position control is often used in unloaded or lightly loaded situations.
SEA joint position control is mainly intended to ensure the consistency of a joint position with a target joint position, and commonly used control methods include proportional differential control (PD control), Linear Quadratic Regulator (LQR) control, and the like. The joint position PD control usually shows faster response speed, high overshoot and longer adjustment time, and the adjustment time of the PD control under the action of load can be further increased and even cause control divergence. The LQR control often makes the SEA joint exhibit equivalent stiffness directly related to the spring stiffness, the overshoot and the adjustment time are generally small, the response time can also reach a certain control requirement under the condition that the hardware selection is proper and the parameter adjustment is reasonable, and the control can endow the joint with flexibility equivalent to the spring stiffness to control the joint, so that the control method can meet the requirement of impact load.
Because the common SEA joint pure position control method is difficult to meet the requirement of position control comprehensive performance of relatively high load, a person skilled in the art needs to develop a general position control method suitable for all linear elastic driving joints urgently, and comprehensive performances such as position control accuracy, response speed, adjusting time and the like of the elastic driving joints under the load condition can be effectively improved.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a position control apparatus and method, a storage medium, and a device for a serial elastic actuator, which solve the problems of low position control accuracy, slow response speed, and long adjustment time of a robot mechanical arm joint in the prior art under a load condition.
In order to solve the above-mentioned technical problem, an embodiment of the present invention provides a position control apparatus for a series elastic actuator, including: a joint controlled object; the sensor is arranged on the joint controlled object and used for detecting the joint position actual value and the equivalent spring deformation of the joint controlled object; the subtractor is used for obtaining a joint position control error according to a joint expected position and the joint position actual value, wherein one input end of the subtractor is connected with the sensor, and the other input end of the subtractor receives the joint expected position; the input end of the PD controller is connected with the output end of the subtracter and used for obtaining a PD output value according to the joint position control error; the inverse multiplier is used for obtaining an equivalent spring deflection gain value according to the equivalent spring deflection, and the input end of the inverse multiplier is connected with the sensor; the adder is used for obtaining speed control quantity of an output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value, wherein one input end of the adder is connected with the output end of the PD controller, and the other input end of the adder is connected with the output end of the inverse multiplier; the input end of the multiplier is connected with the output end of the adder and used for obtaining the speed control quantity of the output shaft of the motor according to the speed control quantity and the reduction ratio of the output shaft of the speed reducer; and the motor system is used for dragging the joint controlled object to move according to the speed control quantity of the motor output shaft, the input end of the motor system is connected with the output end of the multiplier, and the output end of the motor system is connected with the joint controlled object.
The embodiment of the invention also provides a position control method of the series elastic driver, which comprises the following steps: acquiring an actual value of a joint position of a joint controlled object by using a sensor; measuring the equivalent spring deformation of the joint controlled object by using a direct method or an indirect method; calculating an equivalent spring deflection gain value according to the equivalent spring deflection by using a reverse multiplier; obtaining a PD output value according to the expected joint position and the actual joint position value; obtaining speed control quantity of an output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value; obtaining the speed control quantity of the output shaft of the motor according to the speed control quantity and the reduction ratio of the output shaft of the speed reducer; and controlling the motor to drag the joint controlled object to move by using the speed control quantity of the motor output shaft.
Embodiments of the present invention also provide a storage medium having a computer program stored thereon, which, when being executed by a processor, carries out the steps of the method for position control of a series elastic drive.
The embodiment of the invention also provides computer equipment, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor executes the computer program to realize the steps of the position control method of the series elastic driver.
According to the above embodiments of the present invention, the position control device and method, storage medium, and apparatus of the series elastic actuator have at least the following advantages: the amount of deformation of an elastic element of an SEA (series elastic actuator) joint under load is taken into consideration in advance, compensation control is performed based on the amount of deformation, and feedback control is performed based on the actual arrival position and the desired position of the SEA joint, thereby improving the SEA joint position control accuracy, effectively reducing the adjustment time, and obtaining a response time almost equal to that of PD control (proportional differential control).
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description, serve to explain the principles of the invention.
Fig. 1A is a first structural diagram of a conventional series elastic actuator joint.
Fig. 1B is a structural diagram of a conventional tandem elastic actuator joint.
Fig. 1C is a third structural diagram of a conventional series elastic actuator joint.
FIG. 2A is a graph illustrating the deviation between the expected position and the actual position of the joint of the series elastic driver according to an embodiment of the present invention.
FIG. 2B is a schematic diagram of a joint position control of a series elastic actuator according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a first embodiment of a position control apparatus of a series elastic actuator according to an embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a second embodiment of a position control apparatus of a series elastic actuator according to an embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a third embodiment of a position control apparatus of a series elastic actuator according to an embodiment of the present invention.
Fig. 6 is a schematic structural diagram of a fourth embodiment of a position control apparatus of a series elastic actuator according to an embodiment of the present invention.
Fig. 7 is a flowchart of a method for controlling a position of a series elastic actuator according to an embodiment of the present invention.
Description of reference numerals:
1 Joint controlled object 2 sensor
3 subtracter 4 PD controller
5 inverse multiplier 6 adder
7 multiplier 8 motor system
41 proportional gain 42 differentiator
43 speed booster 44 built-in adder
45 built-in subtracter 81 speed reducer
82 motor 83 motor controller
F frame M motor
G speed reducer S elastic element
L-load connecting rod
Detailed Description
For the purpose of promoting a clear understanding of the objects, aspects and advantages of the embodiments of the invention, reference will now be made to the drawings and detailed description, wherein there are shown in the drawings and described in detail, various modifications of the embodiments described herein, and other embodiments of the invention will be apparent to those skilled in the art.
The exemplary embodiments of the present invention and the description thereof are provided to explain the present invention and not to limit the present invention. Additionally, the same or similar numbered elements/components used in the drawings and the embodiments are used to represent the same or similar parts.
As used herein, the terms "first," "second," …, etc., do not denote any order or sequence, nor are they used to limit the present invention, but rather are used to distinguish one element from another or from another element or operation described in the same technical language.
With respect to directional terminology used herein, for example: up, down, left, right, front or rear, etc., are simply directions with reference to the drawings. Accordingly, the directional terminology used is intended to be illustrative and is not intended to be limiting of the present teachings.
As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.
As used herein, "and/or" includes any and all combinations of the described items.
References to "plurality" herein include "two" and "more than two"; reference to "multiple sets" herein includes "two sets" and "more than two sets".
As used herein, the terms "substantially", "about" and the like are used to modify any slight variation in quantity or error that does not alter the nature of the variation. Generally, the range of slight variations or errors modified by such terms may be 20% in some embodiments, 10% in some embodiments, 5% in some embodiments, or other values. It should be understood by those skilled in the art that the aforementioned values can be adjusted according to actual needs, and are not limited thereto.
FIG. 2A is a graph illustrating the deviation of a desired position from an actual position achieved by a tandem elastic actuator (SEA) joint according to an embodiment of the present invention; FIG. 2B is a schematic diagram of a series elastic actuator joint position control scheme according to an embodiment of the present invention, as shown in FIG. 2A, assuming a desired joint position of the SEA joint is
The spring deformation amount can be generated under the action of load
Resulting in the actual value of the joint position of the SEA joint being
The requirements of the SEA joint position control precision under the action of high load cannot be met. To solve the above problem and improve the accuracy of position control of the SEA joint under load, the amount of spring deflection δ' under load can be estimated and a new desired position of the joint can be recalculated from the original desired position
If the SEA joint is under the load action, the spring is deformed by delta', and if the deformation of the spring is accurately estimated, the actual value of the joint position of the SEA joint
Will return to the original joint expected position
As shown in fig. 2B, precise control of the SEA joint position is achieved.
Fig. 3 is a schematic structural diagram of a first embodiment of a position control apparatus of a series elastic actuator according to an embodiment of the present invention, as shown in fig. 3, a subtractor obtains an actual value of a joint position from a sensor, sets a desired joint position in advance, obtains a control error of the joint position by subtracting the actual value of the joint position from the desired joint position, and obtains a PD output value by a PD controller according to the control error of the joint position; the inverse multiplier obtains an equivalent spring deflection gain value according to the equivalent spring deflection; the adder obtains the equivalent spring deflection gain value from the inverse multiplier, and sums the equivalent spring deflection gain value and the PD output value to obtain the speed control quantity of the output shaft of the speed reducer; the multiplier obtains the speed control quantity of the output shaft of the motor (namely the speed control input quantity of the output shaft of the motor) according to the speed control quantity of the output shaft of the speed reducer and the reduction ratio; the motor system drags the joint controlled object to move according to the speed control quantity of the motor output shaft.
In the embodiment shown in the drawing, the position control device of the series elastic driver comprises: a joint controlled object 1, a sensor 2, a subtracter 3, a PD controller 4, an inverse multiplier 5, an adder 6, a multiplier 7, and a motor system 8. Wherein the sensor 2 is arrangedOn the joint controlled object 1, a sensor 2 is used to detect a joint position actual value of the joint controlled object 1
And an equivalent spring deflection δ; a subtracter 3 for estimating the desired position of the joint
And said actual value of the joint position
A joint position control error l is obtained, wherein,
one input end of the subtracter 3 is connected with the sensor 2, and the other input end of the subtracter 3 receives the joint expected position
Actual value of joint position
Also called joint position actual feedback value; the input end of the PD controller 4 is connected with the output end of the subtracter 3, and the PD controller 4 is used for obtaining a PD output value according to the joint position control error; the inverse multiplier 5 is configured to obtain an equivalent spring deflection gain value according to the equivalent spring deflection, that is, the equivalent spring deflection δ is multiplied by a gain k of the inverse multiplier 5 to obtain an equivalent spring deflection gain value k δ, where an input end of the inverse multiplier 5 is connected to the sensor 2, and an output end of the inverse multiplier 5 is connected to an input end of the adder 6; the adder 6 is used for obtaining the speed control quantity omega of the output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value k deltagWherein one input end of the adder 6 is connected with the output end of the PD controller 4, and the other input end of the adder 6 is connected with the output end of the inverse multiplier; an input terminal of the multiplier 7 is connected to an output terminal of the adder 6The multiplier 7 is used for controlling the quantity omega according to the speed of the output shaft of the speed reducergAnd the reduction ratio Gear obtains the speed control quantity omega of the output shaft of the motormdI.e. the reducer input shaft speed control amount, where ωmd＝ωgX Gear; the motor system 8 is used for controlling the quantity omega according to the speed of the output shaft of the motormdDragging the joint controlled object 1 to move, wherein the input end of the motor system 8 is connected with the output end of the multiplier 7, and the output end of the motor system 8 is connected with the joint controlled object 1. In a preferred embodiment of the present invention, the joint controlled object 1(Plant) is a serial elastic driver joint link, a load physical element, or the like; the sensor 2 may be an encoder, and the sensor 2 may detect the equivalent spring deformation amount δ and the joint position actual value of the joint controlled object 1
(i.e., joint angle), etc.
Referring to fig. 3, the deformation amount of the SEA joint under the load is considered in advance, and feedback control is performed according to the actual value of the joint position of the SEA joint and the desired position of the joint, so that the accuracy of the SEA joint position control can be effectively improved, the SEA joint adjustment time can be reduced, and the response time almost equal to that of the PD control can be obtained.
The joint controlled object 1 may be a serial elastic driver joint link. When the deformation direction of the spring (elastic piece) is completely the same as the motion direction of the SEA joint, the equivalent spring deformation delta is the deformation of the spring, and when the deformation direction of the spring is different from the motion direction of the SEA joint, the equivalent spring deformation delta is required to be equivalent according to the specific structure of the SEA joint, so that the equivalent spring deformation delta in the same motion direction as the SEA joint is obtained, and the precise control of the SEA joint is realized.
Fig. 4 is a schematic structural diagram of a second embodiment of a position control apparatus of a series elastic actuator according to an embodiment of the present invention, and as shown in fig. 4, a PD controller may specifically include a proportional gain unit, a differentiator, a speed gain unit, and a built-in adder.
In the embodiment shown in the figure, the PD controller 4 specifically includes a scaling upA summer 41, a differentiator 42, a speed booster 43 and a built-in adder 44. The proportional gain device 41 is configured to perform gain processing on the joint position control error l, wherein an input end of the proportional gain device 41 is connected to an output end of the subtractor 3; the differentiator 42 is used for differentiating the joint position control error l to obtain a joint movement speed error
Wherein the content of the first and second substances,
i.e. joint motion velocity error
Differentiating the joint position control error l with respect to time t, wherein the input end of the differentiator 42 is connected with the output end of the subtracter 3; a velocity booster 43 is used to correct the joint motion velocity error
Performing a gain process, wherein an input of the speed booster 43 is connected to an output of the differentiator 42; the built-in adder 44 is used to find the gain of the joint motion velocity error
And gain of the joint position control error
The sum of the PD output values is obtained and is transmitted to the adder 6, wherein the PD output value is
An input terminal of the internal adder 44 is connected to an output terminal of the proportional booster 41, another input terminal of the internal adder 44 is connected to an output terminal of the speed booster 43, and an output terminal of the internal adder 44 is connected to an input terminal of the adder 6. One preferred tool of the inventionIn one embodiment, the speed control amount ω of the reducer output shaftgMay be as follows
Namely, it is
Speed control quantity omega of input shaft of speed reducermd(i.e., the motor output shaft speed control amount) is ωmd＝ωgX Gear, i.e
Referring to fig. 4, the deformation of the SEA joint under the load is considered in advance, and the desired position of the SEA joint is adjusted from the position layer surface, so that the improvement of the overall performance of the SEA joint position control under the large load is realized.
Fig. 5 is a schematic structural diagram of a third embodiment of a position control apparatus of a series elastic actuator according to an embodiment of the present invention, and as shown in fig. 5, a PD controller may specifically include a proportional gain unit, a differentiator, a speed gain unit, and a built-in subtractor.
In the embodiment shown in the figure, the PD controller 4 specifically includes a proportional gain unit 41, a differentiator 42, a speed gain unit 43 and a built-in subtractor 45. The proportional gain device 41 is configured to perform gain processing on the joint position control error l, wherein an input end of the proportional gain device 41 is connected to an output end of the subtractor 3; a differentiator 42 for determining the actual value of the joint position
Differential processing is carried out to obtain the actual value of the joint velocity
The desired velocity of the joint is usually set to 0, the input of the differentiator 42 and theThe output end of the sensor 2 is connected; a velocity booster 43 for applying an actual value of the joint velocity
Performing gain processing (i.e. performing gain processing on the inverse of the joint velocity error), wherein an input end of the velocity booster 43 is connected with an output end of the differentiator 42; a built-in subtractor 45 for finding the gain of the joint position control error
And a gain of the actual value of the joint velocity
The difference (i.e. the sum of the joint position control error and the joint velocity error) is obtained and fed to the adder 6, wherein the PD output value is
One input terminal of the built-in subtractor 45 is connected to the output terminal of the proportional booster 41, the other input terminal of the built-in subtractor 45 is connected to the output terminal of the speed booster 43, and the output terminal of the built-in subtractor 45 is connected to one input terminal of the adder 6. In a preferred embodiment of the present invention, the speed control amount ω of the reducer output shaftgThe specific calculation formula is
Namely, it is
Speed control quantity omega of input shaft of speed reducermd(i.e., the motor output shaft speed control amount) is ωmd＝ωgX Gear, i.e
Referring to fig. 5, the deformation of the SEA joint under the load is considered in advance, and the desired position of the SEA joint is adjusted from the position layer surface, so that the improvement of the overall performance of the SEA joint position control under the large load is realized.
Fig. 6 is a schematic structural diagram of a fourth embodiment of a position control device of a series elastic driver according to a specific embodiment of the present invention, and as shown in fig. 6, a motor system specifically includes a speed reducer, a motor, and a motor controller, where the speed reducer drives a joint controlled object to move, the motor drives the speed reducer to operate, and the motor controller controls motor transportation according to a speed control amount of a motor output shaft.
In the embodiment shown in the drawing, the motor system 8 specifically includes: a speed reducer 81, a motor 82, and a motor controller 83. The speed reducer 81 is mechanically connected with the joint controlled object 1, and the speed reducer 81 is used for driving the joint controlled object 1 to move through an elastic element; the motor 82 is mechanically connected with the speed reducer 81, and the motor 82 is used for driving the speed reducer 81 to operate; the motor controller 83 is connected with the multiplier 7, and the motor controller 83 is used for controlling the transfer of the motor 82 according to the speed control quantity of the motor output shaft.
Referring to fig. 6, the deformation of the SEA elastic element is considered, and the desired position of the joint is compensated and controlled, so that the joint position control can obtain higher precision, the adjustment time is effectively reduced, the SEA joint position control can be fast and stable, and meanwhile, the response time almost same as that of the PD control can be obtained, and better comprehensive position control performance is obtained.
Fig. 7 is a flowchart of a position control method of a series elastic driver according to an embodiment of the present invention, where the method shown in fig. 7 can be applied to the apparatuses shown in fig. 2A to 6, and obtains an actual value of a joint position of a joint controlled object, and measures an equivalent spring deformation amount thereof; obtaining a PD output value according to the expected joint position and the actual joint position value, and obtaining the speed control quantity of the output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value; then obtaining the speed control quantity of the output shaft of the motor (namely the speed control input quantity of the input shaft of the speed reducer) according to the speed control quantity of the output shaft of the speed reducer; and finally, controlling the motor to drag the joint controlled object to move by using the speed control quantity of the motor output shaft.
In the embodiment shown in the drawing, the position control method of the series elastic driver comprises the following steps:
s101: a joint position actual value of a joint controlled object is acquired by a sensor. In an embodiment of the present invention, the sensor (sensor) may be an encoder; actual value of joint position
Usually expressed in terms of joint angles.
S102: and measuring the equivalent spring deformation of the joint controlled object by using a direct method or an indirect method. In the embodiment of the invention, the method for measuring the equivalent spring deformation amount comprises a direct method and an indirect method.
S103: and calculating an equivalent spring deflection gain value according to the equivalent spring deflection by using an inverse multiplier. In the embodiment of the present invention, the multiplier of the inverse multiplier is k, and the product of the equivalent spring deflection δ and the multiplier k is the equivalent spring deflection gain value k δ.
S104: and obtaining a PD output value according to the expected joint position and the actual joint position value. In the embodiment of the present invention, the difference between the desired joint position and the actual joint position is the PD output value.
S105: and obtaining the speed control quantity of the output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value. In the embodiment of the invention, the sum of the PD output value and the equivalent spring deformation gain value k delta is the speed control quantity of the output shaft of the speed reducer.
S106: and obtaining the speed control quantity of the output shaft of the motor according to the speed control quantity of the output shaft of the speed reducer and the reduction ratio. In the embodiment of the invention, the speed control quantity omega of the output shaft of the speed reducergThe product of the sum and the reduction Gear ratio Gear is the motor output shaft speed control amount omegamd。
S107: and controlling the motor to drag the joint controlled object to move by using the speed control quantity of the motor output shaft. In the embodiment of the present invention, step S107 specifically includes: controlling the rotation of the motor according to the speed control quantity of the motor output shaft; an output shaft of the motor drives the speed reducer to operate; the speed reducer drags the joint controlled object to move through an SEA elastic element.
Referring to fig. 7, considering the deformation of the SEA joint itself under the load, and also considering the deformation amount of the SEA elastic element, and performing compensation control on the desired position of the joint, the SEA joint position control can obtain higher precision, effectively reduce the adjustment time, and can obtain almost the same response time as the PD control, and obtain better comprehensive position control performance.
In a preferred embodiment of the present invention, the step of measuring the equivalent spring deformation of the joint controlled object by using a direct method specifically includes: acquiring the actual position of the output shaft of the motor through a motor high-speed end incremental encoder; obtaining a reduction ratio by a reduction gear characteristic; obtaining the actual position of the output shaft of the speed reducer according to the actual position of the output shaft of the motor and the reduction ratio; acquiring an actual value of the joint position through a joint end absolute encoder; and obtaining the equivalent spring deformation according to the actual position of the output shaft of the speed reducer and the actual value of the joint position.
As the flexibility of the elastic element (such as a small-stiffness spring) of the SEA joint is generally far smaller than that of the motor reducer (particularly a harmonic reducer), the actual position of the output shaft of the reducer is defaulted
And desired position of joint
Are the same, so that the equivalent spring deformation can be considered as the actual position of the output shaft of the speed reducer
And actual value of joint position
A difference of (i.e. an equivalent spring deformation amount of)
Therefore, the motor height can be adjustedThe motor output shaft actual position that the fast end incremental encoder obtained, joint position actual value and the gear ratio calculation equivalent spring deflection that the joint end absolute encoder obtained are exactly: according to the actual position of the output shaft of the motor obtained by the incremental encoder at the high-speed end of the motor, the actual position of the output shaft of the speed reducer is obtained by combining the reduction ratio Gear
Obtaining the actual value of the joint position according to the absolute encoder of the joint end
Equivalent spring deflection
In a preferred embodiment of the present invention, the step of measuring the equivalent spring deformation of the joint controlled object by an indirect method specifically includes: measuring the torque of the joint of the series elastic driver; calculating the equivalent stiffness of the joint according to the stiffness coefficient of the elastic element and the characteristic parameters of the joint structure; and calculating the deformation of the equivalent spring according to the moment and the equivalent stiffness of the joint.
Specifically, the moment tau of the SEA joint is measured, the equivalent spring deformation delta is indirectly obtained according to the equivalent stiffness Ks of the joint,
the joint moment tau can be measured by adding an additional moment sensor, and for an SEA joint formed by an elastic element (flexible element) with higher rigidity, the joint moment tau can also be measured by attaching a strain gauge and the like; the joint equivalent stiffness Ks can be obtained by converting the stiffness coefficient of the elastic element and different structural characteristic parameters of the SEA joint, and the joint equivalent stiffness Ks is generally a fixed parameter.
In a preferred embodiment of the present invention, the step of measuring the moment of the joint of the series elastic driver specifically includes: and measuring the torque of the joint of the series elastic driver by using a torque sensor or a strain gauge.
The present invention also provides a storage medium having a computer program stored thereon, the computer program, when executed by a processor, implementing a method for controlling a position of a series elastic actuator, the method comprising the steps of:
s101: a joint position actual value of a joint controlled object is acquired by a sensor.
S102: and measuring the equivalent spring deformation of the joint controlled object by using a direct method or an indirect method.
S103: and calculating an equivalent spring deflection gain value according to the equivalent spring deflection by using an inverse multiplier.
S104: and obtaining a PD output value according to the expected joint position and the actual joint position value.
S105: and obtaining the speed control quantity of the output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value.
S106: and obtaining the speed control quantity of the output shaft of the motor according to the speed control quantity of the output shaft of the speed reducer and the reduction ratio.
S107: and controlling the motor to drag the joint controlled object to move by using the speed control quantity of the motor output shaft.
The embodiment of the present invention further provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements a position control method for a series elastic driver when executing the computer program, and the method includes the following steps:
s101: a joint position actual value of a joint controlled object is acquired by a sensor.
S102: and measuring the equivalent spring deformation of the joint controlled object by using a direct method or an indirect method.
S103: and calculating an equivalent spring deflection gain value according to the equivalent spring deflection by using an inverse multiplier.
S104: and obtaining a PD output value according to the expected joint position and the actual joint position value.
S105: and obtaining the speed control quantity of the output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value.
S106: and obtaining the speed control quantity of the output shaft of the motor according to the speed control quantity of the output shaft of the speed reducer and the reduction ratio.
S107: and controlling the motor to drag the joint controlled object to move by using the speed control quantity of the motor output shaft.
The embodiments of the invention described above may be implemented in various hardware, software code, or combinations of both. For example, an embodiment of the present invention may also be program code for executing the above method in a Digital Signal Processor (DSP). The invention may also relate to a variety of functions performed by a computer processor, digital signal processor, microprocessor, or Field Programmable Gate Array (FPGA). The processor described above may be configured according to the present invention to perform certain tasks by executing machine-readable software code or firmware code that defines certain methods disclosed herein. Software code or firmware code may be developed in different programming languages and in different formats or forms. Software code may also be compiled for different target platforms. However, the different code styles, types, and languages of software code and other types of configuration code that perform tasks in accordance with the present invention do not depart from the spirit and scope of the present invention.
The foregoing is merely an illustrative embodiment of the present invention, and any equivalent changes and modifications made by those skilled in the art without departing from the spirit and principle of the present invention should fall within the protection scope of the present invention.
Claims (7)
1. A position control device for a tandem elastic actuator, the device comprising:
a joint controlled object (1);
a sensor (2) which is arranged on the joint controlled object (1) and is used for detecting the joint position actual value and the equivalent spring deformation of the joint controlled object (1);
the subtracter (3) is used for obtaining a joint position control error according to a joint expected position and the joint position actual value, wherein one input end of the subtracter (3) is connected with the sensor (2), and the other input end of the subtracter (3) receives the joint expected position;
the input end of the PD controller (4) is connected with the output end of the subtracter (3) and used for obtaining a PD output value according to the joint position control error;
the inverse multiplier (5) is used for obtaining an equivalent spring deflection gain value according to the equivalent spring deflection, wherein the input end of the inverse multiplier (5) is connected with the sensor (2);
the adder (6) is used for obtaining speed control quantity of an output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value, wherein one input end of the adder (6) is connected with the output end of the PD controller (4), and the other input end of the adder (6) is connected with the output end of the inverse multiplier (5);
the input end of the multiplier (7) is connected with the output end of the adder (6) and is used for obtaining the speed control quantity of the output shaft of the motor according to the speed control quantity and the speed reduction ratio of the output shaft of the speed reducer; and
the motor system (8) is used for dragging the joint controlled object (1) to move according to the motor output shaft speed control quantity, the input end of the motor system (8) is connected with the output end of the multiplier (7), the output end of the motor system (8) is connected with the joint controlled object (1),
the equivalent spring deformation is obtained by measuring the joint controlled object (1) by a direct method or an indirect method,
the method comprises the following steps of measuring the equivalent spring deformation of the joint controlled object (1) by using a direct method, and specifically comprises the following steps:
acquiring the actual position of the output shaft of the motor through a motor high-speed end incremental encoder;
obtaining a reduction ratio according to the speed reducer characteristics;
obtaining the actual position of the output shaft of the speed reducer according to the actual position of the output shaft of the motor and the reduction ratio;
acquiring an actual value of the joint position through a joint end absolute encoder; and
obtaining the equivalent spring deformation according to the actual position of the output shaft of the speed reducer and the actual value of the joint position,
the method comprises the following steps of measuring the equivalent spring deformation of the joint controlled object by an indirect method, and specifically comprises the following steps:
measuring the torque of the joint of the series elastic driver;
calculating the equivalent stiffness of the joint according to the stiffness coefficient of the elastic element and the characteristic parameters of the joint structure; and
and calculating the deformation of the equivalent spring according to the moment and the equivalent stiffness of the joint.
2. The device for controlling the position of a series elastic actuator according to claim 1, characterized in that the PD controller (4) comprises in particular:
the proportional gain device (41) is used for performing gain processing on the joint position control error, wherein the input end of the proportional gain device (41) is connected with the output end of the subtracter (3);
a differentiator (42) for performing differential processing on the joint position control error to obtain a joint movement speed error, wherein an input end of the differentiator (42) is connected with an output end of the subtracter (3);
a velocity booster (43) for gain processing the articulation velocity error, wherein an input of the velocity booster (43) is connected to an output of the differentiator (42);
and the built-in adder (44) is used for obtaining the sum of the gain of the joint movement speed error and the gain of the joint position control error to obtain the PD output value, wherein one input end of the built-in adder (44) is connected with the output end of the proportional gain device (41), the other input end of the built-in adder (44) is connected with the output end of the speed gain device (43), and the output end of the built-in adder (44) is connected with one input end of the adder (6).
3. The device for controlling the position of a series elastic actuator according to claim 1, characterized in that the PD controller (4) comprises in particular:
a proportional gain device (41) for performing gain processing on the joint position control error, wherein an input end of the proportional gain device (41) is connected with an output end of the subtracter (3);
a differentiator (42) for performing differential processing on the joint position actual value to obtain a joint velocity actual value, wherein an input end of the differentiator (42) is connected with an output end of the sensor (2);
a speed gain device (43) for performing gain processing on the joint speed actual value, wherein an input end of the speed gain device (43) is connected with an output end of the differentiator (42);
and the built-in subtracter (45) is used for obtaining the difference between the gain of the joint position control error and the gain of the joint speed actual value to obtain the PD output value, wherein one input end of the built-in subtracter (45) is connected with the output end of the proportional gain device (41), the other input end of the built-in subtracter (45) is connected with the output end of the speed gain device (43), and the output end of the built-in subtracter (45) is connected with one input end of the adder (6).
4. The tandem elastic actuator position control apparatus according to claim 1, wherein the joint controlled object (1) is a tandem elastic actuator joint link.
5. A method of controlling the position of a series elastic actuator, the method comprising:
acquiring an actual value of a joint position of a joint controlled object by using a sensor;
measuring the equivalent spring deformation of the joint controlled object by using a direct method or an indirect method;
calculating an equivalent spring deflection gain value according to the equivalent spring deflection by using a reverse multiplier;
obtaining a PD output value according to the expected joint position and the actual joint position value;
obtaining speed control quantity of an output shaft of the speed reducer according to the PD output value and the equivalent spring deformation gain value;
obtaining the speed control quantity of the output shaft of the motor according to the speed control quantity and the reduction ratio of the output shaft of the speed reducer; and
controlling the motor to drag the joint controlled object to move by using the speed control quantity of the motor output shaft,
the method for measuring the equivalent spring deformation of the joint controlled object by using the direct method comprises the following steps:
acquiring the actual position of the output shaft of the motor through a motor high-speed end incremental encoder;
obtaining a reduction ratio according to the speed reducer characteristics;
obtaining the actual position of the output shaft of the speed reducer according to the actual position of the output shaft of the motor and the reduction ratio;
acquiring an actual value of the joint position through a joint end absolute encoder; and
obtaining the equivalent spring deformation according to the actual position of the output shaft of the speed reducer and the actual value of the joint position,
the method comprises the following steps of measuring the equivalent spring deformation of the joint controlled object by an indirect method, and specifically comprises the following steps:
measuring the torque of the joint of the series elastic driver;
calculating the equivalent stiffness of the joint according to the stiffness coefficient of the elastic element and the characteristic parameters of the joint structure; and
and calculating the deformation of the equivalent spring according to the moment and the equivalent stiffness of the joint.
6. A storage medium having stored thereon a computer program which, when being executed by a processor, carries out the steps of the method as claimed in claim 5.
7. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the method of claim 5 when executing the computer program.
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