Numerical and Experimental Analysis of a Parallel 2-DOF Manipulator

A parallel two degrees of freedom manipulator designed for a variable orientation of a body in space is analyzed. The manipulator consists of one universal joint with one axis fixed to the base and the other axis fixed to a moving platform. A similar device is used in spacecraft to orient the rocket nozzle. In this work, two parallel linear hydraulic actuators move the platform. A novel proportional digital hydraulic valve is used to control the actuators. Each fork of the universal joint has an angular position sensor mounted to measure the relative motion of the cross and an inertial measurement unit (IMU) is fixed to the moving platform. Load cells and pressure transducers are mounted on the actuators to measure force and chambers pressure. Numerical simulations are presented using a desired trajectory as input for a proportional controller (P-controller). An experimental apparatus is used to validate the numerical results.