| During process of fruit picking with agricultural robots, it is easy to damage the fruit, if the grasping force is too.large and easy to slip if the grasping force is too small since fruit is easily deformed it was required that the end-effectors work with compliance for non-damage in the course of grasping fruit and vegetable. Active Compliance control, i.e., force control, was adopted in this study to reduce the possible damage of fruits and vegetables. In the picking or grasping process. The completed work is generalized as follows:1) To meet the experiment requirements of control system based on slip feeling, the original experiment platform of automatic grasping system for fruit and vegetable was reformed,. The reformed platform was consisted of end-effector, control card, data acquisition card, AC servo motor, PVDF slide tactile sensor, charge amplifier AC servo driver, force sensor, signal amplifier, regulated power, industrial computer, et al. In this way, the open architecture force control system of end-effector was built up based on PC. The system has good expansibility, generality and practicability, and the requirements for precision force control of end-effector can be satisfied.2) One kind of control algorithm suitable for fruit and vegetable grasping based on slippery+strength outer ring control method was proposed. A slipping tactile sensor was used to obtain the minimum grasping force. Then the deviation of measured practical grasping force with the minimum value was converted to digital input speed control command. With the force deviation decreasing the end-actuator decelerated to stop. The algorithm can reduce the force overshoot and oscillation and make the fruit stably grasped without damage.3) Experiments were carried out to investigate the performance of the control algorithm based on slippage tactile+the outer ring force control method, The results show that the algorithm is feasible and successful rate of capture is high with such control algorithm. |
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