Abstract
In this paper, we propose a torque measurement device embedded in robot arms. The device uses an integrated microdisplacement sensor and trapezoidal frame. The sensor tip of 3 mm area and 0.7 mm thickness measures the mirror tilt angle on the underside of the frame caused by a torque applied to the frame. We have successfully measured a linear output change for the torque and found that the gradient of the output change differed largely from the material and the corner angle of the frame.
Highlights
In recent works, torque sensors have been used to control electro power steering (EPS) in cars to detect torque applied to a steering wheel, where the torque is detected through measurement of a magnetic change in a torsion bar without a contact.[1,2,3] Magnetictype torque sensors have the advantage of robustness and remarkable resolution, yet they have a weakness associated with electromagnetic noise.[4]
Torque sensors have been used to control electro power steering (EPS) in cars to detect torque applied to a steering wheel, where the torque is detected through measurement of a magnetic change in a torsion bar without a contact.[1,2,3] Magnetictype torque sensors have the advantage of robustness and remarkable resolution, yet they have a weakness associated with electromagnetic noise.[4]. There have been other types of torque sensors that exploit strain gauges[5,6,7,8,9,10] and optics.[4,11] Hashimoto et al have reported torque sensors using strain gauges to detect the dynamic torque applied to a harmonic drive.[8,9,10] These torque sensors, which use magnetic change, strain gauges, and optics, are tiny and maintain high accuracy; they are applicable to robot arms
Robot arms are driven by an axial torque output by reducers, and this torque cannot be calculated through a product of the motor-generated torque and a reduction gear ratio since they are unequal owing to the friction generated at the reducers
Summary
Torque sensors have been used to control electro power steering (EPS) in cars to detect torque applied to a steering wheel, where the torque is detected through measurement of a magnetic change in a torsion bar without a contact.[1,2,3] Magnetictype torque sensors have the advantage of robustness and remarkable resolution, yet they have a weakness associated with electromagnetic noise.[4]. There are three approaches to detect axial torque output by reducers: disturbance observer, a wrist 6-axis force sensor, and an articular torque sensor. A disturbance observer is a method that deduces an external unknown or uncertain disturbance torque without the use of an additional sensor. This technique is widely used for industrial robots.[12,13,14] This method is unable to achieve high accuracy, yet is cheap to implement. An articular torque sensor can precisely detect a tiny external force, even if the force is applied at a midpoint of an arm. The articular torque sensor is better suited for external torque sensing
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