Wearable Robot Torque Control via Motor Current and Acceleration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wearable robots require expensive and heavy force/torque sensors to precisely control the manipulation of high-load objects, which increases costs and weight, necessitating a more affordable and lightweight solution for torque detection.
Innovation Solution
A method that measures current variations in the motor joints of a wearable robot, combined with data from an acceleration sensor, to calculate the intended manipulation torque of the user, allowing for precise control without the need for expensive sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force/torque sensor is mounted between the gripper and the handle to precisely detect manipulation torque and weight, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces the mechanical force/torque sensor system with an electrical measurement system. Specifically, it uses current sensors to detect motor current variations and acceleration sensors to detect gravitational acceleration, then calculates torque and weight through computational processing. This substitution of mechanical sensing with electrical sensing and computational analysis resolves the contradiction by achieving precise measurement without complex mechanical sensor assemblies.
Solution Approach 2:
The patent introduces current variation as an intermediary parameter to indirectly measure manipulation torque. Instead of directly measuring torque with a force sensor, the system measures the current variation in motor drivers, which serves as an intermediate indicator that can be computationally converted into torque information. This intermediary approach simplifies the sensing system while maintaining measurement precision.
2Measurement precision
If a force/torque sensor is installed to accurately measure weight and torque, then measurement precision is improved, but the weight of the wearable robot increases
Solution Approach 1:
The patent replaces heavy mechanical force/torque sensors with lightweight electrical current sensors and acceleration sensors. The weight measurement is achieved not by direct mechanical sensing but by detecting gravitational acceleration through acceleration sensors and computing weight from the relationship between acceleration, current variation, and known system parameters. This substitution dramatically reduces the weight of the wearable robot while maintaining accurate weight detection capability.
Solution Approach 2:
The patent uses acceleration sensors to detect gravitational effects as a copy or proxy for direct weight measurement. Instead of mechanically measuring the force of gravity acting on the object, the system detects the acceleration caused by gravity and uses this information, combined with current variation data, to compute the weight. This indirect copying approach reduces hardware weight while preserving measurement accuracy.
3Measurement precision
If a precise force/torque sensor is used to detect manipulation torque, then measurement precision is improved, but cost increases significantly
Solution Approach 1:
The patent replaces expensive force/torque sensors with much cheaper current sensors and acceleration sensors. The core innovation lies in using the existing motor drivers' current measurements, which are already part of the robot's control system, combined with acceleration sensor data, to compute manipulation torque through signal processing and calculation. This substitution with inexpensive electrical sensors and computational methods dramatically reduces manufacturing cost while maintaining precise torque detection.
Solution Approach 2:
The patent makes the motor drivers serve a dual function: both actuating the joints and sensing the current for torque estimation. By utilizing the existing motor driver current measurements for torque detection purposes, the system eliminates the need for separate expensive torque sensors. This self-service approach, where existing components perform multiple functions, reduces overall system cost while maintaining measurement precision.
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
Enables precise control of wearable robots at a lower cost by using acceleration sensors and current variations to determine user torque, reducing the weight and expense of sensor systems.
Implementation Method 1
computing an external force caused by the weight object using both an acceleration measured by an acceleration sensor when a user applies an operating force to a handle of the robot
Implementation Method 2
measuring a variation in the current in the motor of each joint of a wearable robot, and calculating a torque at each joint
Data Source
AI summary
Disclosed herein is a method of obtaining the intended manipulation torque of a user for a wearable robot. The method allows the wearable robot, the motion of each joint of which is operated by a motor and which is capable of measuring a variation in current in the motor of each joint and calculating a torque at each joint, to simply and rapidly extract the intended manipulation torque of the user using both an acceleration value (e.g., measured by an acceleration sensor installed on a gripper), and the current variation of the motor, in a state in which the wearable robot does not know the weight of a weight object to be lifted with the gripper. Accordingly, the wearable robot may be suitably controlled at a comparatively lower cost.