Robot Appendage Slip Recovery via Dynamic Force Control
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Solution Overview
Problem
Legged robots face challenges in traversing slippery surfaces due to slip events, which degrade their kinematic and energetic performance, leading to potential loss of balance and reduced efficiency in movement.
Innovation Solution
The system dynamically adjusts forces applied to a robot appendage by determining an appendage position and a filter position, calculating the distance between them, and applying a force based on this distance, with the filter position being adjusted if the distance exceeds a threshold to effectively mitigate slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the robot applies force to the appendage to arrest slip movement, then the slip mitigation effectiveness is improved, but the risk of over-correction increases
Solution Approach 1:
The control system continuously monitors the distance between the appendage position and filter position, using this feedback to dynamically adjust the applied force. When the distance exceeds the threshold, force is applied to arrest slip; when the distance is within the threshold, force is reduced or eliminated to prevent over-correction. This closed-loop feedback mechanism resolves the contradiction by adapting the control force to real-time slip conditions.
Solution Approach 2:
The system dynamically adjusts the filter position threshold based on current slip conditions rather than using a fixed threshold. The filter position is updated iteratively to track the appendage movement while maintaining an appropriate distance threshold. This dynamic adaptation allows the system to optimize slip mitigation effectiveness while avoiding over-correction across varying operational conditions.
2Measurement precision
If the filter position is dynamically adjusted to track appendage movement, then the slip detection accuracy is improved, but the system complexity increases
Solution Approach 1:
The filter position serves as an intermediary variable that indirectly represents the appendage position while filtering out noise and minor variations. Instead of directly using raw sensor measurements, the system maintains a filter position that tracks the general trend of appendage movement. This intermediary approach improves slip detection accuracy by providing a smoothed reference while avoiding the complexity of sophisticated filtering algorithms.
Solution Approach 2:
The filter position is initialized to represent the initial touchdown position of the appendage before slip occurs. This preliminary setup establishes a reference point that enables immediate slip detection when the appendage moves beyond the threshold distance. By preparing the filter position in advance and updating it iteratively, the system achieves accurate slip detection without requiring complex real-time computation.
Data Source
AI summary
The disclosure provides systems and methods for mitigating slip of a robot appendage. In one aspect, a method for mitigating slip of a robot appendage includes (i) receiving an input from one or more sensors, (ii) determining, based on the received input, an appendage position of the robot appendage, (iii) determining a filter position for the robot appendage, (iv) determining a distance between the appendage position and the filter position, (v) determining, based on the distance, a force to apply to the robot appendage, (vi) causing one or more actuators to apply the force to the robot appendage, (vii) determining whether the distance is greater than a threshold distance, and (viii) responsive to determining that the distance is greater than the threshold distance, the control system adjusting the filter position to a position, which is the threshold distance from the appendage position, for use in a next iteration.