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TSM 363 Fluid Power Systems

TSM 363 Fluid Power Systems. Electronic Controls in Hydraulics Systems. Automated Functions – A Technical Trend. E/H Systems (Conventional Design). M. Controller. M. E/H Systems (Programmable Design). M. Controller. M. Basic Electrical Devices.

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TSM 363 Fluid Power Systems

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  1. TSM 363 Fluid Power Systems Electronic Controls in Hydraulics Systems

  2. Automated Functions – A Technical Trend

  3. E/H Systems (Conventional Design) M Controller M

  4. E/H Systems (Programmable Design) M Controller M

  5. Basic Electrical Devices Seven devices commonly used in the control of electrohydraulic systems: • Push-button switches • Limit switches • Pressure switches • Drivers (Servo or Solenoids) • Relays • Timers • Temperature switches

  6. Operator control Input Signal time Valve control E/H Control Valves • On/Off solenoid • Proportional Solenoid • Low cost • PWM control of the solenoid • Advanced controls • Servo Valves • Torque motors • Costly, limited applications

  7. Option 1: Solenoid E/H Valve

  8. 1. Traditional air-gap type proportional solenoid driver 2. Wet-armature type proportional solenoid driver Commonly Used Proportional Solenoid Drivers

  9. Pulse-Width Modulation (PWM) Signal

  10. Va Vs Solenoid Characteristics of PWM Signals • Amplifier acts as a variable resistance to power solenoid • Voltage fully-on • Amplifier has zero resistance, no heat build-up • Maximum voltage to solenoid • Voltage fully-off • No power to amplifier, no heat buildup • High pulse-rate signal of full-on/full-off • Pulse rate is faster than the solenoid can react • Solenoid sees these as an average voltage

  11. Option 2: Two Stage E/H Valve

  12. Option 3: Servo E/H Valve • Servo mechanism • Electric motor • Position feedback potentiometer • Reduction gear • Actuator arm

  13. Output Input E/H Valve Actuator Open Loop Control Circuits • Simple circuit with no measurement of the performance at various settings

  14. Closed-Loop Control • Feedback enhances performance • Dynamic response and stability reference command + System dynamics output Controller - feedback

  15. Example of E/H Controls

  16. Properties of Valve Response: Deadband

  17. Properties of Valve Response: Saturation

  18. Properties of Valve Response: Hysteresis

  19. Properties of Valve Response: Stability Response Time

  20. Lecture Summary • Discussed the basic principles of electro-mechanical drivers for E/H valves: • Solenoid driver • Servo driver • Introduced a few key parameters describing the performance of an E/H valve: • Deadband • Saturation • Hysteresis

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