Serial Manipulator Touch Localization Using Joint Torque Estimation
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Solution Overview
Problem
Current collision detection and collision avoidance systems for serial manipulators, particularly in domestic applications, are inadequate due to the high cost and maintenance requirements of tactile sensors and the inability of torque sensors to accurately locate touch points.
Innovation Solution
A touch sensing method for serial manipulators that utilizes torque sensors and processing units to calculate Jacobian matrices and estimate joint torques, allowing for the localization of external touches by determining the link connected to the joint with the minimum error between measured and estimated torque values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tactile sensors are used to detect collision and touch, then measurement precision is improved, but device cost and maintenance requirements increase
Solution Approach 1:
The patent replaces tactile sensors (mechanical contact-based detection) with torque sensors that measure joint torques to detect collisions. Instead of using mechanical/electronic skin sensors at the end effector, the system uses torque measurements at the joints combined with dynamic modeling (Jacobian matrices, Coriolis forces, centrifugal forces) to infer collision information, thereby avoiding the cost and maintenance issues of tactile sensors while maintaining collision detection capability
Solution Approach 2:
The patent introduces torque sensors as intermediary measurement devices and uses dynamic model calculations (Jacobian matrices, Coriolis and centrifugal force compensation) as a mediator to translate joint torque measurements into collision detection information. This intermediary approach allows indirect collision detection without requiring direct contact sensors at the end effector
2Device complexity
If torque sensors are used to detect collision, then device cost is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where torque sensor measurements are continuously fed into dynamic model calculations, and the calculated collision information is used to adjust and refine the collision detection algorithm. The system uses feedback from joint torque measurements combined with dynamic modeling to iteratively improve touch point localization accuracy, compensating for the simpler sensor setup
Solution Approach 2:
The patent changes the measurement parameters from direct contact force (tactile sensors) to joint torque (torque sensors), and compensates by incorporating dynamic parameters (Coriolis forces, centrifugal forces, Jacobian matrices) into the calculation model. This parameter transformation allows the system to achieve accurate collision detection using torque measurements instead of direct force measurements
3Measurement precision
If the number of tactile sensors is increased to obtain high spatial resolution, then measurement precision is improved, but device cost and complexity increase
Solution Approach 1:
The patent transitions from spatial distribution of multiple tactile sensors (2D/3D sensor array on end effector surface) to temporal-dynamic dimension by using torque measurements over time combined with dynamic modeling. Instead of adding sensors in space, the system uses the dynamic characteristics of the manipulator (mass matrix, Coriolis matrix, centrifugal matrix, Jacobian matrix) to achieve spatial resolution through mathematical modeling of the entire system's dynamics
Data Source
AI summary
A touch sensing method and a serial manipulator using the same are disclosed. A serial manipulator using the method may detect and localize external torques by obtaining a torque value of each joint of a serial manipulator through a torque sensor at the joint; obtaining a preset joint angle of each joint from the serial manipulator; calculating a Jacobian matrices of the serial manipulator based on the joint angle of the joints; estimating joint torques of the serial manipulator based on the torque value of each joint and the Jacobian matrices; calculating an error between the torque value of each joint and the estimated joint torque corresponding to the joint; and determining a link of the serial manipulator that is connected to the joint with the minimum calculated error as having been touched.