Compositional impedance programming for robots
Described herein are concepts, techniques, and structures for robot control using compositional impedance programming. In one embodiment, a robot control system comprises a plurality of impedance modules, each of the impedance modules defining one or more mechanical impedance parameters and an impedance controller.
1. A robot control system comprising:
a plurality of impedance modules, each of the impedance modules defining one or more mechanical impedance parameters; and
an impedance controller implemented in a processor and configured to:
generate a composite robot control law based on at least some of the plurality of impedance modules;
receive an actual robot configuration and an actual robot configuration-space velocity;
generate an actuator torque using the composite robot control law, the actual configuration of a robot and the actual configuration-space velocity of the robot; and
control actuators of the robot according the actuator torque;
wherein:
a first one of the plurality of impedance modules defines an impedance control law for an end-effector of the robot;
a second one of the plurality of impedance modules drives the robot to a selected base configuration; and
a third one of the plurality of impedance modules defines an impedance control law for a joint of the robot.
2. The system of claim 1 wherein the third one of the impedance modules defines an impedance control law for an elbow of the robot.
3. The system of claim 1 wherein the impedance controller is further configured to transform the impedance control law for the end-effector from Cartesian-space to robot configuration-space.
4. The system of claim 1 wherein the impedance controller is configured to take into account external forces when generating the actuator torque.
5. The system of claim 1 wherein one or more of the plurality of impedance modules are energetically passive.
6. The system of claim 1 wherein a first one of the plurality of impedance modules defines a control law for a first robot and a second of the plurality of impedance modules defines a control law for a second robot different from the first robot.
7. The system of claim 1 wherein at least one of the plurality of impedance modules defines one or more impedance parameters for a damped spring.
8. A method for controlling a robot, the method comprising:
selecting impedance parameters for each of a plurality of impedance modules, wherein each of the plurality of impedance modules specifies a robot behavior associated with a task, wherein each of the impedance modules and its selected impedance parameters define an impedance control law and wherein a first one of the impedance modules defines an impedance control law for an end-effector of the robot; a second one of the impedance modules drives the robot to a selected base configuration; and a third one of the impedance modules defines an impedance control law for a joint of the robot;
transforming, via a processor, one or more of the impedance module control laws into configuration space;
generating, via a processor, a composite control law using the impedance module controls laws in configuration-space; and
controlling the robot, via a processor, using the composite control law.
9. The method of claim 8 wherein at least one of the plurality of impedance modules defines a damped spring control law to manipulate an object using an end-effector of the robot.
10. The method of claim 8 wherein at least one of the plurality of impedance modules defines a damped spring control law to manipulate an object using an elbow of the robot.
11. The method of claim 8 wherein at least one of the plurality of impedance modules imposes a base joint stiffness on the robot.
12. The method of claim 8 wherein selecting impedance parameters for each of a plurality of impedance modules includes selecting, for at least one of the plurality of impedance modules, a resting position, a stiffness, and a damping coefficient for a damped spring control law.
13. The method of claim 8 wherein selecting impedance parameters for each of a plurality of impedance modules includes selecting, for at least one of the plurality of impedance modules, a base joint stiffness for the robot.
14. The method of claim 13 wherein selecting the base joint stiffness for the robot includes selecting a base joint stiffness to reduce apparent end-effector mass normal to an object's surface.