Robot Collision Detection Using Temperature-Adaptive Thresholds
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Solution Overview
Problem
Existing robot collision detection methods rely on costly sensors or temperature-dependent threshold adjustments, leading to potential erroneous detection due to viscous friction coefficient errors, especially at low temperatures, which can increase the risk of collision misclassification.
Innovation Solution
A method that uses a temperature sensor integrated with the motor encoder to dynamically adjust the collision detection threshold based on internal temperature readings, reducing erroneous detection by recalculating the threshold when the internal temperature exceeds a certain level, thereby minimizing the impact of high viscous friction coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a collision sensor is used to detect collision, then collision detection accuracy is improved, but system cost increases and the sensor becomes a heavy load that slows down the robot and consumes more energy
Solution Approach 1:
The patent replaces the mechanical collision sensor with a computational approach using motor current detection and dynamic calculation. The collision detection system uses the motor's electrical characteristics (current, torque, inertia) and dynamic models to calculate collision forces, eliminating the need for physical collision sensors and their associated mechanical components.
Solution Approach 2:
The patent introduces motor current as an intermediary parameter to indirectly detect collision forces. Instead of directly measuring collision with a sensor, the system uses motor current measurements combined with dynamic calculations to infer collision information, serving as a non-intrusive mediator that doesn't add mechanical load.
2Measurement precision
If the collision detection threshold is adjusted based on temperature, then detection accuracy at low temperature is improved, but the system complexity increases due to additional temperature sensors and wiring
Solution Approach 1:
The patent makes the existing motor encoder serve multiple functions: it not only detects motor position for control purposes but also provides temperature information for collision detection threshold adjustment. This multi-functional use eliminates the need for separate temperature sensors and reduces system complexity.
Solution Approach 2:
The motor encoder performs self-service by providing both position and temperature data needed for collision detection. The system uses its own existing components (motor, encoder, current measurements) to gather all necessary information for adaptive threshold adjustment, without requiring external temperature sensing infrastructure.
3Reliability
If the collision detection threshold is increased to prevent erroneous detection at low temperature, then false collision detection is reduced, but actual collision detection sensitivity decreases
Solution Approach 1:
The patent implements dynamic adjustment of the collision detection threshold based on real-time temperature conditions. The threshold is not fixed but adapts dynamically: increased at low temperatures to prevent false detection, and decreased at normal temperatures to maintain high sensitivity. This dynamic approach resolves the contradiction between reliability and sensitivity.
Solution Approach 2:
The system changes the detection threshold parameter according to temperature conditions. By adjusting this critical parameter based on environmental temperature, the system optimizes both false detection prevention and collision sensitivity, transforming a static threshold into a condition-dependent variable.
Data Source
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AI summary
Collision of a robot is detected by the following method. The robot includes a motor, a gear reducer connected to the motor, an encoder detecting a rotation of the motor, a temperature sensor installed to the encoder, and an object which is driven by the motor via the gear reducer. An external force torque due to a collision as a collision torque estimation value is estimated by subtracting a dynamic torque obtained by an inverse dynamic calculation of the robot from a torque output to the gear reducer by the motor. It is determined that the robot receives an external force if the collision torque estimation value is greater than a predetermined collision detection threshold. The predetermined collision detection threshold is set to a first value in a case where a temperature detected by the temperature sensor is less than a predetermined temperature threshold. The predetermined collision detection threshold is set to a second value less than the first value at a first time point at which the detected temperature is equal to or greater than the predetermined temperature threshold in a case where a maximum value of the collision torque estimation value is less than a first maximum value determination threshold in a period to the first time point from a second time point prior to the first time point by a predetermined length of time. The predetermined collision detection threshold is set to the first value at the first time point in a case where the maximum value of the collision torque estimation value is equal to or greater than the first maximum value determination threshold in the period.