Actuators and sensors

Abstract

In this chapter, two basic robot components are treated: actuators and sensors. In the first part, the features of an actuating system are presented in terms of the power supply, power amplifier, servomotor and transmission. In view of their control versatility, two types of servomotors are used, namely, electric servomotors for actuating the joints of small and medium size manipulators, and hydraulic servomotors for actuating the joints of large size manipulators. The models describing the input/output relationship for such servomotors are derived, together with the control schemes of the drives. The electric servomotors are also employed to actuate the wheels of the mobile robots, which will be dealt with in Chap. 11. Successively, proprioceptive sensors are presented which allow measurement of the quantities characterizing the internal state of the manipulator, namely, encoders and resolvers for joint position measurement, tachometers for joint velocity measurement; further, exteroceptive sensors are presented including force sensors for end-effector force measurement, distance sensors for detection of objects in the workspace, and vision sensors for the measurement of the characteristic parameters of such objects, whenever the manipulator interacts with the environment.