 Humanoid robots use accelerometers to measure the acceleration, from which velocity can be calculated by integration; tilt sensors to measure inclination; force sensors placed in robot's hands and feet to measure contact force with environment; position sensors, that indicate the actual position of the robot (from which the velocity can be calculated by derivation) or even speed sensors.Arrays of tactels can be used to provide data on what has been touched.The Shadow Hand uses an array of 34 tactels arranged beneath its polyurethane skin on each finger tip.