Robot control
A method for controlling a mechanical system having a plurality of components interlinked by a plurality of driven joints, the method comprising: measuring torques or forces about or at the driven joints and forming a load signal representing the measured torques or forces; receiving a motion demand signal representing a desired state of the system; implementing an impedance control algorithm in dependence on the motion demand signal and the load signal to form a target signal indicating a target configuration for each of the driven joints; measuring the configuration of each of the driven joints and forming a state signal representing the measured configurations; and forming a set of drive signals for the joints by, for each joint, comparing the target configuration of that joint as indicated by the target signal to the measured configuration of that joint as indicated by the state signal.
1. A method for controlling a mechanical system having a plurality of components interlinked by a plurality of driven joints, the method comprising:
measuring torques or forces about or at the driven joints and forming a load signal representing the measured torques or forces;
receiving a motion demand signal representing a desired state of the system;
implementing an impedance control algorithm in dependence on the motion demand signal and the load signal to form a target signal indicating a target configuration for each of the driven joints;
measuring the configuration of each of the driven joints and forming a state signal representing the measured configurations; and
forming a set of drive signals for the joints by, for each joint, comparing the target configuration of that joint as indicated by the target signal to the measured configuration of that joint as indicated by the state signal.
2. A method as claimed in claim 1 , comprising driving each of the driven joints in dependence on the respective drive signal.
3. A method as claimed in claim 2 , wherein each of the driven joints is provided with a respective electric motor for driving motion at the joint and each drive signal is applied to the respective electric motor.
4. A method as claimed in claim 2 , comprising repeatedly performing the measuring the configuration step, the forming the set of drive signals step and the driving step.
5. A method as claimed in claim 4 , wherein the step of forming the set of drive signals is performed at higher frequency than the step of forming the target signal.
6. A method as claimed in claim 1 , wherein the impedance control algorithm is implemented in dependence on, for each driven joint, a respective mass, damper and spring term.
7. A method as claimed in claim 6 , comprising:
receiving data representing desired impedance characteristics for the physical system in a first coordinate space; and
converting that data to, for each driven joint, a respective mass, damper and spring term.
8. A method as claimed in claim 1 , wherein the motion demand signal represents a desired configuration for each of the driven joints.
9. A method as claimed in claim 8 , wherein the first coordinate space is a non-Cartesian coordinate space; a topological space or a vector space.
10. A method as claimed in claim 8 , comprising:
receiving a primary motion demand signal representing a desired physical position of a part of the mechanical system;
performing an inverse kinematic computation to determine a configuration for each of the driven joints that would position the part of the mechanical system at the desired physical position; and
providing those configurations as the motion demand signal.
11. A method as claimed in claim 1 , wherein forming a target signal is performed using joint space.
12. A method as claimed in claim 1 , wherein the motion demand signal represents a desired physical position of a part of the mechanical system.
13. A method as claimed in claim 12 , wherein the said step of implementing the impedance control algorithm comprises:
implementing the impedance control algorithm to determine a target physical position of the part of the mechanical system;
performing an inverse kinematic computation to determine a configuration for each of the driven joints that is suitable for positioning the part of the mechanical system at the target physical position; and
forming the target signal as indicating those configurations as the target configurations for the driven joints.
14. A method as claimed in claim 13 , comprising:
specifying additional information indicating a desired configuration of the mechanical system; and
the step of performing an inverse kinematic computation is performed so as to determine a configuration for each of the driven joints that is suitable for positioning the part of the mechanical system at the target physical position and satisfying the desired configuration specified by the additional information.
15. A method as claimed in claim 1 , comprising converting the measured torques or forces about or at the driven joints to a first coordinate space different from the space in which they were measured so as to form the load signal.
16. A method as claimed in claim 15 , wherein the first coordinate space is a non-Cartesian space; a topological space or a vector space.
17. A method as claimed in claim 1 , wherein the mechanical system is a robot manipulator.
18. A method as claimed in claim 1 , wherein the mechanical system is a master-slave manipulator and the motion demand signal is formed by a master controller.
19. A controller for a mechanical system having a plurality of components interlinked by a plurality of driven joints, the controller being configured to:
measure torques or forces about or at the driven joints and forming a load signal representing the measured torques or forces;
receive a motion demand signal representing a desired state of the system;
implementing an impedance control algorithm in dependence on the motion demand signal and the load signal to form a target signal indicating a target configuration for each of the driven joints;
measure the configuration of each of the driven joints and forming a state signal representing the measured configurations; and
form a set of drive signals for the joints by, for each joint, comparing the target configuration of that joint as indicated by the target signal to the measured configuration of that joint as indicated by the state signal.
20. A non-transitory computer readable storage medium having stored thereon processor-executable instructions that, when executed at a computer system, cause the computer system to control a mechanical system having a plurality of components interlinked by a plurality of driven joints, the processor-executable instructions configured to cause the computer system to:
measure torques or forces about or at the driven joints and forming a load signal representing the measured torques or forces;
receive a motion demand signal representing a desired state of the system;
implementing an impedance control algorithm in dependence on the motion demand signal and the load signal to form a target signal indicating a target configuration for each of the driven joints;
measure the configuration of each of the driven joints and forming a state signal representing the measured configurations; and
form a set of drive signals for the joints by, for each joint, comparing the target configuration of that joint as indicated by the target signal to the measured configuration of that joint as indicated by the state signal.