Man-Power-Amplifying Exoskeleton with Pneumatic Actuator

Abstract

This study describes the activity of developing a force amplifier exoskeleton with one degree of freedom. The system was developed as a research prototype to conduct control system studies. The device consists of an arm with a pneumatic cylinder actuator controlled by a pressure regulator. As for the human–machine interface, the system has a force sensor. The idea is to verify the possibility of developing a simple system from the sensor system’s point of view and the control system’s architecture while simultaneously obtaining an effective, economical, and reliable device. The idea developed in this project is to use the user’s available ability to control movements in unknown environments. The user constitutes the central part of the entire control system: he defines the references for the speeds and forces to be applied to the environment and observes the rates of the controlled robotic system through his own sight and proprioceptive system. On the other hand, the machine produces and controls the forces applied to the environment by the actuator. In this way, the device shows an increased admittance. A mathematical system model was created to verify the idea’s feasibility. Following the results of the simulations, a prototype was built on which experimental tests were carried out. As stated above, it was possible to obtain the described behavior with the use of a force sensor, one-axis type, interposed between the machine and the user, to constitute the human–machine interface; using a pressure regulator, it was possible to avoid the sensors for the force feedback by the environment. The result is a simple architecture for the sensors and the control algorithm. Specific test protocols were proposed to test the performance of the human–machine “system”, and a test bench was developed that allows the tracking of variable signals represented on a monitor, which the user must follow. The system is intuitive to use, with a rapid learning curve, and the user can handle high loads according to the different signals to be followed with good precision, even at high speeds.