Tham khảo tài liệu 'sensors, focus on tactile, force and stress sensors 2011 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Torque Sensors for Robot Joint Control 21 6. Influence from any of the nontorsional components of load should be canceled to guarantee precise measurement of torque T that is moment around Z-axis MZ in 6-axis sensors. 7. Behavior of the sensing element output and mechanical structure should be as close to linear as possible. 8. Simple to manufacture low-cost and robust. Optical approaches of torque measurement satisfy the demands of compact sizes light in weight and robustness. The small influence of electrical noise created by DC motors on output signal of optical sensors results in high signal-to-noise ratio and sensor resolution. Therefore we decided to employ this technique to measure torque in robot joints. Design of new optical torque sensors The novelty of our method is application of the ultra-small size photointerrupter PI as sensitive element to measure relative motion of sensor components. The relationship between the output signal and position of the shield plate for RPI-121 ROHM is shown in Fig. 5. The linear section of the transferring characteristic corresponding approximately to mm is used for detection of the relative displacement of the object. The dimensions of the photointerrupter RPI-121 X X mm and weight of g enable realization of compact sensor design. Two mechanical structures were realized to optimize the sensor design the in-line structure where detector input and output are displaced axially by the torsion component and the in plane one where sensor input and output are disposed in one plane and linked by bending radial flexures. The layout of the in-line structure based on a spring with a cross-shaped cross section is shown in Fig. 6. This spring enables large deflections without yielding. The detector consists of input part 1 output part 2 fixed PI 3 shield 4 and cross-shaped spring 5. The operating principle is as follows when torque T is applied to the input shaft the spring is deflected rotating the shield 4.