Robotic Force Torque Sensor Temperature Compensation
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Solution Overview
Problem
Robotic force/torque sensors face inaccuracies due to thermal drift caused by ambient temperature changes, self-heating, and mechanical stresses, which are challenging to compensate for effectively using existing technologies.
Innovation Solution
Individual temperature compensation of strain gages using thermal sensors mounted proximate to each gage, with initial and post-temperature change outputs used to calculate coefficients for a temperature compensation equation, allowing for accurate estimation of force and torque values by processing these coefficients with a least squares algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gages are used to measure force and torque in a robotic sensor, then measurement capability is provided, but temperature-related errors cause inaccuracy in measurements
Solution Approach 1:
The patent divides the temperature compensation process into individual strain gage-level compensation rather than system-level compensation. Each strain gage has its own temperature compensation equation with coefficients determined by its specific thermal characteristics, allowing precise correction of temperature-induced errors for each sensing element independently
Solution Approach 2:
The patent changes the parameters of the strain gage output by introducing temperature compensation equations that adjust the measured signals based on temperature data. By calculating compensation coefficients from initial outputs at known loads and temperatures, then applying these coefficients to correct subsequent measurements, the system transforms temperature-drifted signals into accurate force and torque readings
2Measurement precision
If thermal sensors are mounted proximate to each strain gage for temperature compensation, then temperature measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent applies local quality by placing thermal sensors proximate to each individual strain gage rather than using a single remote temperature sensor. This local placement allows each strain gage to be compensated based on its specific thermal environment, capturing temperature gradients and localized thermal effects that would be missed by a single centralized sensor
Solution Approach 2:
The system performs self-service temperature compensation by using the strain gage outputs themselves (along with local thermal sensor data) to determine their own compensation coefficients. Each strain gage's initial output at known loads and temperatures is used to calculate its specific compensation parameters, allowing the sensor to self-correct for temperature effects without external calibration equipment
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
The proposed solution significantly reduces temperature-related errors, improving the accuracy of force and torque measurements in robotic force/torque sensors, bringing temperature errors within 1% of full scale error under various temperature conditions.
Implementation Method 1
Strain gages affixed to some or all surfaces of each beam generate an electrical signal proportional to the deformation experienced by the beam
Implementation Method 2
thermal sensors measuring the temperature of the MAP and TAP
Data Source
AI summary
Strain gages on a robotic force/torque sensor are individually temperature compensated prior to resolving the gage outputs to estimate force and torque loads on the sensor. Thermal sensors are mounted proximate each strain gage, and the initial gate and thermal sensor outputs at a known load and temperature are obtained. The force/torque sensor then undergoes warming, and strain gage and thermal sensor outputs are again obtained. These gage and thermal sensor outputs are processed to calculate coefficients to a temperature compensation equation, such as by using a least squares algorithm. Each strain gage output is compensated using the temperature compensation equation, and the temperature-compensated outputs of the strain gages are then combined to resolve temperature-compensated force and torque values.