Robotic Arm Force Feedback Control for Safe Contact Transitions
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Solution Overview
Problem
Traditional direct force feedback controllers for robots face issues such as joint limit exceedance and potential damage when transitioning between contact and non-contact states with the environment, due to rapid force responses.
Innovation Solution
A direct force feedback control method that calculates impedance and force control components using a mass-spring-damper model and force selection matrices, allowing for precise force control by projecting joint data into Cartesian space and adjusting control quantities based on actual and expected forces, ensuring smooth movement and safe contact detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional direct force feedback control is used with rapid response, then force control precision is improved, but joint limits are quickly exceeded and damage may occur during contact transitions
Solution Approach 1:
The control method applies preliminary anti-action by detecting contact state transitions in advance and pre-adjusting control parameters. When contact is detected, the controller proactively reduces force feedback gain and adjusts impedance parameters before the robot can exceed joint limits or cause damage, thereby preventing the harmful effect while maintaining force control precision during stable contact phases
Solution Approach 2:
The invention implements dynamics by making control parameters adaptive rather than fixed. The controller dynamically adjusts force feedback gain, impedance parameters, and damping coefficients based on real-time contact state detection. This allows the system to maintain high force control precision during contact while preventing joint limit exceedance during transition phases, effectively resolving the contradiction between precision and safety
2Measurement precision
If force feedback gain is increased for better control precision, then force control accuracy is improved, but excessive force appears when in contact with environment
Solution Approach 1:
The control method uses feedback by continuously monitoring contact state and force magnitude, then adjusting force feedback gain accordingly. When contact force exceeds a threshold or during contact transitions, the controller reduces the gain to prevent excessive force application. This feedback mechanism maintains high control accuracy during normal operation while automatically preventing harmful excessive forces during contact
Solution Approach 2:
The invention applies parameter changes by dynamically modifying force feedback gain and impedance parameters based on contact state. The controller switches between different parameter sets: high gain for precision during non-contact or stable contact, and reduced gain during contact transitions or when excessive force is detected. This resolves the contradiction by allowing high accuracy when safe and reducing force when contact occurs
Data Source
AI summary
A direct force feedback control method as well as a controller and a robot using the same are provided. The method includes: obtaining an actual position and an actual speed of an end of the robotic arm and an actual external force acting on the end in a Cartesian space; calculating an impedance control component of the end in the Cartesian space based on the obtained actual position, the obtained actual speed, the obtained actual external force, an expected position, an expected speed, and an expected acceleration of the end; calculating a force control component of the end in the Cartesian space based on an expected interaction force acting on the end, the actual external force, and the actual speed; determining whether the actual external force is larger than a preset threshold, and obtaining a total force control quantity of the end of the robotic arm in the Cartesian space.