Robot Force Control With Adaptive MPC Horizon Switching
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Solution Overview
Problem
Existing force control processing for control targets, such as robots, tends to be time-consuming and can be further accelerated.
Innovation Solution
A control system and method that utilizes model predictive control to adjust the prediction and control horizons based on the state of contact with an object, either before or after vibration settles, thereby optimizing the control process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If model predictive control is used to determine manipulative variables for force control, then control precision is improved, but processing time increases
Solution Approach 1:
The patent dynamically adjusts the prediction horizon length based on the contact state between the control target and object. When vibration is detected during contact, the prediction horizon is extended to capture the vibration period, allowing the MPC to effectively suppress vibrations while maintaining fast processing through adaptive horizon adjustment rather than using a consistently long horizon
Solution Approach 2:
The patent changes the prediction horizon parameter according to the contact state. By detecting whether the control target is in contact with an object and identifying vibration states, the system adjusts the prediction horizon length to match the actual dynamic conditions, achieving both precision and speed by using longer horizons only when necessary for vibration suppression
2Stability of the object's composition
If the prediction horizon is extended to capture vibration periods, then vibration suppression capability is improved, but calculation complexity increases
Solution Approach 1:
The prediction horizon is made dynamic rather than fixed. The system adjusts the horizon length based on detected contact states and vibration characteristics, extending the horizon only when vibrations are present and reducing it when contact is stable, thereby managing calculation complexity adaptively while maintaining vibration suppression capability
Solution Approach 2:
The system uses feedback from contact state detection and vibration analysis to adjust the prediction horizon. By continuously monitoring the contact between the control target and object and detecting vibration patterns, the system provides feedback to the MPC controller to modify the prediction horizon, creating a closed-loop system that balances vibration suppression with computational efficiency
Data Source
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AI summary
Disclosed herein is a technique for speeding up processing concerning the force control of a control target. A control system (1) performs control about a motion path of a control target (such as a robot Rb1) along which the control target possibly makes direct or indirect contact with an object (9). The control system (1) includes a model predictive controller (3), a determiner (21), and an adjustor (22). The model predictive controller (3) determines, using model predictive control, a manipulative variable to bring external force applied from the object (9) to the control target at a time of the contact into agreement with target force. The determiner (21) determines whether a state of the contact of the control target (such as a robot Rb1) with the object (9) at a first point in time is a first state or a second state. The first point in time is either simultaneous with, or later than, a second point in time when vibration is produced by the contact of the control target with the object (9). The first state is a state before the vibration settles. The second state is a state after the vibration has settled. The adjustor (22) adjusts, in accordance with a decision made by the determiner (21), a horizon length of at least one horizon selected from the group consisting of a prediction horizon and a control horizon. Both the prediction horizon and the control horizon are applied to the model predictive control.