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The strength part of the drive consists from two pneumatic cylinders which can act on the mechanical control target (CT - moving platform of VMMR), electro-pneumatic control unit (ECU) and supply pressure device. In ECU consists of following elements:
● Valve V, that can change the direction of movement
● The group of valves V1…VN that can switch-on or switch-off the throttles
● The throttles T1...TN on the exhaust, that determine the speed of the pistons in cylinder and connected CT
The informational part of the drive represented with position sensor that measures the control target position. Position sensor can be continuous or can represent the set of on-off sensors, for example, sealed contacts or Hall sensors. Computer control unit (CCU) is the PLC or another control device that has the ADC converter for the position sensor and the set of digital outputs that can generate signals for on-off valves in the electro-pneumatic
control unit.
The number of valves determine amount of the braking stages, the flow rates of throttles determine the intense of braking. These characteristics are chosen according to the features of specific task and drive requirements. The experience in these drives usage shows that for majority of tasks it is enough to have two or three stages braking.
Fig. 2. VMMR drive structure for massive objects movement.
The main role of movement management is assigned to hardware and software parts of computer control unit. This unit executes the algorithm which uses the information from position sensor. The algorithm forms binary signals on valves in real-time. That allows reaching the main goal – high-speed and smooth movement of massive object without shocks and rebounds in the end of movement.
The schematic diagram of the strength part of the drive is represented on Fig. 3.
Fig. 3. The schematic diagram of the strength part of the drive.
Where:
- C1 and C2 – pneumatic magnetic cylinders without internal braking systems, that means without damping seal, plug and without screw at the cap.
- S1…S6 – the set of on-off sensors with electric output. These sensors can be integrated in the body of cylinder.
Each sensor determine the moment of switching-off the throttle in according valve.
- V – closed centered valve 5/3 structure, that provide changing of direction of pneumatic cylinders and emergency closing of chambers.
- T3 and T6 – throttles, that acting in the second braking stage while moving in and moving out.
- V1, V2, V4, V5 – valves 2/2 structure, that provide switching off the throttles T1, T2, T4, T5 from the exhaust chamber when the signal from sensors S1, S2, S4, S5 is reached. Valves V1 and V2 switching off throttles T1 and T2 on a signal from sensors S1 and S2 when the platform with weight 70 kg is moving (moving in), valves V4 and V5 switching off throttles T4 and T5 on a signal from sensors S4 and S5 when the platform with weight 30 kg is moving (moving out).
- T7 – inlet throttle.
Moving out is provided by generating signals on the valves V4, V5 and left coil of V, so all three throttles – T4, T5, T6 – are connected with the exhaust chamber. When the signal from sensor S4 is reached, throttle T4 is switching off. And when the signal from sensor S5 is reached, throttle T5 is switching off. As a result, piston reaches the front cap with only one connected throttle – T6.