Telescopic Robot Arm Contact Detection Using Position Sensing
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Solution Overview
Problem
Existing torque sensors in collaborative robots struggle to accurately distinguish between contact forces from humans or objects and motion-induced forces due to fluctuations in arm movement, particularly in linear motion mechanisms with freely moving elements.
Innovation Solution
A robot apparatus with a position identification unit using a laser displacement gauge to determine the positions of linear motion elements relative to a fixed element, enabling accurate estimation of the center of gravity and separation of contact forces from motion-induced forces, employing a control device to execute programs for contact detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque sensor is used to detect contact forces in a linear motion mechanism with freely moving elements, then contact detection capability is provided, but measurement precision deteriorates due to fluctuations in arm movement and inability to accurately calculate motion-induced torque
Solution Approach 1:
The patent segments the torque measurement into two independent components: motion-induced torque (calculated from position data of multiple linear motion elements) and contact torque (measured by torque sensor after subtracting motion-induced torque). This segmentation allows accurate contact force detection despite the presence of freely moving elements that cause arm movement fluctuations.
Solution Approach 2:
The patent introduces position detection means (encoders or laser displacement gauges) as intermediary devices to measure the position of each linear motion element. These position measurements serve as mediators to calculate the motion-induced torque, which is then subtracted from the total torque to isolate the contact force component.
2Measurement precision
If position detection means are added to track each linear motion element, then measurement precision of contact forces improves, but device complexity increases
Solution Approach 1:
The control device serves multiple functions: it controls the movement drive mechanism, processes position data from all position detection means, calculates motion-induced torque, and determines contact forces. This multi-functionality consolidates the system architecture and reduces the need for separate dedicated components for each function.
Solution Approach 2:
The patent replaces direct mechanical measurement of contact force with a computational approach using position data and torque calculations. Instead of using complex mechanical linkages or additional force sensors, the system uses electronic position detection and mathematical computation to determine contact forces, thereby reducing mechanical complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the accuracy of contact detection by separating contact forces from motion-induced forces, ensuring safe operation by reliably detecting human or object contact with the robot.
Implementation Method 1
a laser displacement gauge to determine the positions of the linear motion elements
Implementation Method 2
using a laser displacement gauge to determine the positions
Data Source
AI summary
A robot apparatus includes: an arm part including a fixed element 54 and a plurality of linear motion elements assembled in multiple stages extendably with respect to the fixed element; a movement drive mechanism for driving movement of a foremost linear motion element among the plurality of linear motion elements; and a position identification unit for identifying a position of at least one linear motion element of the plurality of linear motion elements other than the foremost linear motion element with respect to the fixed element or the foremost linear motion element.