Robot Manipulator Force-Impedance Control for Contact Loss Stability
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Solution Overview
Problem
Current robotic manipulator control methods, such as purely impedance-controlled and hybrid position-force control, face challenges in accurately exerting forces on environments without precise modeling and are prone to large movements when contact is lost, leading to instability and inefficiency.
Innovation Solution
A device and method for controlling a robot manipulator with a combination of force and impedance controllers, utilizing external force sensing and estimation, and a controller-shaping function to manage manipulated variables, ensuring stable and compliant interaction with environments, even in unmodeled conditions, and preventing dangerous movements upon contact loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If purely impedance control is used to operate in unmodeled environments, then adaptability to unmodeled environments is improved, but force accuracy deteriorates
Solution Approach 1:
The patent merges impedance control and force control into a unified hybrid controller. The controller combines the impedance control component (for adaptability to unmodeled environments) with the force control component (for accurate force application). This integration allows the system to simultaneously achieve adaptability to unknown environments and precise force control, resolving the contradiction between these two requirements.
2Force
If feedforward control with large predetermined force is used, then force application capability is improved, but safety deteriorates due to large movements upon contact loss
Solution Approach 1:
The patent implements feedback control by continuously monitoring the actual contact force and comparing it with the desired force. The controller adjusts the control input based on the feedback signal, ensuring that force is applied accurately while preventing large movements upon contact loss. The feedback mechanism allows the system to respond to contact loss conditions and adjust the force application accordingly, maintaining safety while preserving force capability.
3Measurement precision
If hybrid position-force control is used to exert precise forces, then force accuracy is improved, but robustness to contact loss deteriorates
Solution Approach 1:
The patent implements dynamic control by continuously adapting the controller parameters and control strategy based on the current system state and environmental conditions. The controller dynamically adjusts between position control and force control modes, and modifies control gains based on contact status. This dynamic adaptation enables the system to maintain both force accuracy during contact and robustness during contact loss, resolving the contradiction between these two requirements.
Data Source
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AI summary
The invention relates to a device and method for performing open-loop and closed-loop control of a robot manipulator which is driven by a number M of actuators ACTm and has an end effector. The invention comprises a first unit (101) which registers and/or makes available an external force winder formula (I) acting on the end effector, a regulator (102) which is connected to the first unit (101) and to the actuators ACTm and which comprises a first regulator R1, which is a force regulator, and a second regulator R2 which is connected thereto and which is an impedance regulator, an admittance regulator, a position regulator or a cruise controller, wherein the regulator (102) determines manipulated variables um(t) with which the actuators ACTm can be actuated in such way that when contact occurs with the surface of an object, the end effector acts on said object with a predefined force winder formula (II); where um(t) = um , R 1(t) + um ,R2(t), wherein the first regulator R1 is embodied and configured in such a way that the manipulated variable um,R1(t) is determined as a product of a manipulated variable um,R1(t)* and a function S(v(t)) or as a function S*(v(t), um,R1(t)*) , where um,R1(t) = S(v(t)) um,R1(t)* oder um,R1(t) = S*(v*(t), um,R1(t)*); Formula (III)