Capacitive measurement for robot z-axis position
Permanent address of the item is
Kapasitiivinen mittaus robotin z-suuntaiseen positioon
This Master of Science thesis presents mechanical, electrical, measurement and software design and implementation for robot end effector with capacitive tactile force sensor. This end effector is designed to measure both touch and force in z-axis direction and then used in automated testing of smart devices. Various mechanical and electrical designs can be used in the design of a tactile force sensor. The chosen design is always application driven. Selection of measurement technology and decisions made during the design are dependent on the use case and the demands of the application. Different technologies are introduced and one of them is chosen. The selection is justified on the base of preferred attributes. The designed tactile sensor, with changeable spring steel flexure sheets, is a proof of concept that force sensing can be made affordable and capacitive technology can be used in it. The sensor with 0.1 mm thick spring steel flexure pair is capable to measure forces from 0 g to 70 g with resolution of 2.36g, precision of 1 g, hysteresis of 0.5% and linearity error of ± 1%. In touch sensing of the surface in the direction of z-axis, the sensor performs reliably under 3 milliseconds. In force sensing, the previously used methods have always leaned towards commercial solutions which are often expensive and the new design offers an alternative option for this.