Patent ID: 7178448

Claim:
A method for controlling an air servo cylinder apparatus that includes a cylinder having a piston for driving a pressurizing member for work, servo valves individually connected to respective pressure chambers on the head side and the rod side of the cylinder, pressure sensors for detecting the pressures in the respective pressure chambers, a position sensor for detecting operational positions of the cylinder, and a controller outputting control signals to the two servo valves based on detected signals from the pressure sensors and the position sensor, the method comprising, in the control by the controller, the following processes: an advancing process of advancing the piston up to a target position where the pressurizing member is to contact work; and a pressuring process of subsequently applying a required pressurizing force to the work, wherein, in the advancing process, in a state where the servo valve on the head side is opened to the air intake side while the servo valve on the rod side is opened to the exhaust side, the piston starts to be driven; thereafter, the servo valve on the head side is controlled in accordance with a deviation between a measured pressure of the pressure chamber on the head side by the corresponding pressure sensor and a pressure when clamping, and the servo valve on the rod side is left opened to the exhaust side, the valve opening degree thereof is adjusted to become a valve opening degree in accordance with a deviation of the current position of the piston from the target position, whereby the piston is smoothly decelerated as it approaches the target; and wherein, in the pressurizing process, the pressures in the two pressure chambers in the cylinder are compared based on signals from the pressure sensors, and at the point in time when the pressure in the pressure chamber on the head side has become higher than the pressure in the pressure chamber on the rod side, the servo valve on the rod side is fully opened toward the exhaust side, whereby compressed air in the pressure chamber on the rod side is rapidly discharged.