Coordinated joint motion control system with position error correction

A hydraulic machine control system for controlling a hydraulically actuated mechanical arm to perform a desired task, the mechanical arm comprising a support, multiple links, and an end effector, the end effector being a work implement supported by the links for movement relative to the support, multiple joints connecting the multiple links one to another, to the support and to the end effector, each joint being movable to different joint positions to effect relative movement of the members connected by the respective joint, and multiple controllable actuators to effect the joint movements, wherein the hydraulic machine control system is configured to control the actuators to move the end effector and comprises:

• a number of selectable virtual machine kinematics configurations providing end effector trajectory families for performing different tasks;
• an operator interface comprising operator input devices, the operator interface enabling an operator to select a desired one of the virtual machine kinematics configurations for the movement of the end effector and to define a desired trajectory within the virtual kinematics of the end effector movement in real time to perform the desired task;
• a joint control system configured to:
• generate an input control vector for each link from a control signal vector outside of a closed negative feedback loop, each input control vector comprising, at each of a series of system-determined time intervals, a reference position for each link according to the virtual differential kinematics configuration for the desired trajectory;
• adjust the control signal vector with an error correction vector, if any, supplied through the closed negative feedback loop;
• and
• generate an output position vector based upon measurements of the actual position of each link at each respective time interval under operation of the actuators according to the adjusted control signal vector;
• a dynamic joint model module configured to determine a dynamic motion model of the motion of each link of the mechanical arm by relating for each link the elements of the input control vector to the elements of the output position vector to provide time-variable constant coefficients for each time interval, wherein the dynamic motion model incorporates dynamics components including acceleration;
• and
• a position and velocity error corrector configured to update the error correction vector using the dynamic motion model and differences between measured actual link positions from the output position vector and corresponding reference position positions from the input control vector;
• and
• wherein the joint control system is configured to apply the error correction vector in the closed negative feedback control loop.

A method of controlling a mechanical arm, the method comprising:

• determining initial control signals;
• supplying the initial control signals to an actual machine control sub-system that incorporates an error-correction feedback loop and to a virtual machine model outside of the error-correction feedback loop;
• with the virtual machine model outside of the error-correction feedback loop, determining a reference position vector that results from applying the supplied initial control signals to the virtual machine model;
• with the actual machine control sub-system that incorporates the error-correction feedback loop:
• combining the supplied initial control signals with error-correction signals, if any, supplied through the error-correction feedback loop;
• using the combined control signals to control the mechanical arm;
• measuring results of using the combined control signals to control the mechanical arm;
• determining an actual position vector from the measured results;
• updating the error-correction signals depending on the actual position vector, the reference position vector, and a dynamic motion model of the mechanical arm, wherein for current operating conditions the dynamic motion model reconciles differences between the actual position vector and the reference position vector to provide time-variable coefficients for the dynamic motion model, and wherein the dynamic motion model incorporates dynamics components including acceleration;
• and
• supplying the error-correction signals as part of the error-correction feedback loop for combination with initial control signals.