Robotic Arm Impedance Control With Direction-Decoupled Force Tracking
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Solution Overview
Problem
Impedance control methods for torque-controlled robotic arms face directional coupling issues in Cartesian space, leading to inaccurate force control and deviation from desired trajectories due to inertial matrix coupling, which complicates control and safety in human-robot interaction.
Innovation Solution
An impedance control method that decouples directions by using force sensor information and environmental data to correct the impedance control law, calculating a corrected desired trajectory, and compensating nonlinear terms in real time to achieve precise control and simplify control complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If impedance control is performed in Cartesian space for torque-controlled robotic arms, then flexibility and suitability for interactive occasions are improved, but directional coupling occurs due to inertial matrix coupling, causing inaccurate force control and trajectory deviation
Solution Approach 1:
The patent segments the control problem by separating position control and force control into independent directional components. By decomposing the inertial matrix coupling into individual directional elements, the system can control each direction independently, eliminating the directional coupling effect that causes force control inaccuracy and trajectory deviation.
Solution Approach 2:
The patent changes the control parameters by transitioning from traditional Cartesian space impedance control to a modified control space that accounts for directional independence. This parameter transformation allows the system to maintain flexibility for interactive occasions while achieving accurate force control by adjusting how inertial effects are compensated in each direction separately.
2Speed
If torque control is used instead of position control, then response speed and safety are improved, but control complexity increases due to full dynamics consideration and high nonlinearity
Solution Approach 1:
The patent extracts and isolates the nonlinear dynamic effects from the overall control system. By separating the complex full dynamics considerations into specific manageable components, the system can implement torque control with fast response while reducing control complexity through targeted compensation strategies rather than handling all dynamic effects simultaneously.
Solution Approach 2:
The patent implements feedback mechanisms that continuously monitor system state and adjust control torques in real-time. This feedback approach enables the system to handle the high nonlinearity of torque-controlled robotic arms by dynamically compensating for dynamic effects, maintaining fast response speed while managing control complexity through adaptive correction rather than complex open-loop control.
Data Source
AI summary
An impedance control method as well as a controller and a robot using the same are provided. The method includes: obtaining joint motion information and joint force information in the joint space of a robotic arm and an actual interaction force acting on an end-effector, and calculating actual motion information of the end-effector in the task space based on the joint motion information; calculating a corrected desired trajectory using environment information and a desired end-effector interaction force, and calculating the impedance control torque based on the joint force information, the actual interaction force, the actual motion information, and desired end-effector information including the corrected desired trajectory and determining a compensation torque based on a nonlinear term in a constructed dynamics equation so as to perform a joint torque control on the robotic arm based on the impedance control torque and the compensation torque.