Mitsubishi MR-508XL Especificações descarregar pdf (Página 36)

7.36

Bimba Position Control System

Application Sizing

Assumptions used for Sizing Values recommendations:

• Values shown in sizing table are with no overshoot. If overshoot is acceptable for your application, the deadband may

possibly be less than specified. However, be sure your system cannot go unstable.

• PFC cylinder with Option L is used. (Option L has very low friction seals. The standard PFC utilizes a rod wiper which

increases friction significantly, which will have adverse effects on positioning capabilities).

• 80 psi air supply.

• Minimum of 23.5 VDC provided to the PCS.

• Clean Command Signal for Main Control. (<5mV noise/ripple)

• Leak free system (The system will actually perform well with some system leakage, however, the best performance

is with no leakage).

• Hard air lines (nylon) between the valves and the actuator.

• No backlash in the system.

• Horizontally guided load. The system can handle vertical or inclined loads and still meet the minimum deadband

specified above, however, the velocity may be effected by up to 40%.

• Short air lines allow for better accuracy.

Typical “Rules of Thumb”:

• Deviations from the recommended parameters, such as air pressure, power supply voltage, external friction, etc, will

negatively effect system performance. However, the system may still perform adequately for your application.

• Applications with loads less than 10% of actuator capacity and strokes greater than 4 inches will yield better

repeatability than the minimum deadband shown in the sizing table above.

• Reducing actuator velocity by use of Flow Controls may enable the deadband to be adjusted tighter for a given

application. The Flow Controls must be inserted into the exhaust ports of the valve manifold, NOT in the actuator.

• Oversizing the actuator for a given application typically yields better repeatability.

• Generically, following are relative influences on velocity:

– As Mass increases, Velocity decreases (up to 20%)

– As Friction increases, Velocity decreases (up to 20%)

– As Pressure decreases, Velocity decreases (up to 20%)

• Increased Friction decreases repeatability. Maximum external friction should not exceed 20% of the maximum rated

payload. Any external friction in the application will degrade system performance. Ensure the system is aligned

properly to any guiding systems. Misalignment will cause external application friction.

• A borderline solution can be effective through any/all of the following:

– sacrificing performance in one area for another,

– limiting velocity with external flow controls,

– employing a small central portion of a longer probe,

– using a larger bore cylinder.

• The PCS system is not suited for applications where accurate velocity control is needed by controlling the rate

of command signal change. Flow controls can be used if lower velocities are required.

Do not allow the PCS valves to stay on for prolonged time periods unless the valves

are well ventilated, as they may overheat potentially causing damage to the valves.

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Mitsubishi MR-508XL Especificações Página 36