Which control strategy switches the control signal abruptly between two distinct limits and uses hysteresis to avoid chattering?

Which control strategy switches the control signal abruptly between two distinct limits and uses hysteresis to avoid chattering?

• A. Proportional Controller
• B. Derivative Controller
• C. On-Off Controller
• D. Integral Controller

Answer: (C)

The main idea is a bang-bang control with a deadband. An On-Off controller drives the actuator to one of two extreme states, not a varying output. To prevent rapid flipping, it uses hysteresis: you switch on when the process variable crosses a lower threshold and switch off only after it crosses an upper threshold (or the reverse). This creates a clear gap between the two switching points, so small fluctuations around the switch point won’t cause chattering. A familiar example is a thermostat that turns a heater on at a low temperature and off at a higher temperature, keeping the room within a comfortable range without continuous on/off cycling. Proportional, derivative, and integral controllers adjust outputs continuously based on error, rate of change, or accumulated error, rather than jumping between two fixed limits with a deadband.

The main idea is a bang-bang control with a deadband. An On-Off controller drives the actuator to one of two extreme states, not a varying output. To prevent rapid flipping, it uses hysteresis: you switch on when the process variable crosses a lower threshold and switch off only after it crosses an upper threshold (or the reverse). This creates a clear gap between the two switching points, so small fluctuations around the switch point won’t cause chattering. A familiar example is a thermostat that turns a heater on at a low temperature and off at a higher temperature, keeping the room within a comfortable range without continuous on/off cycling. Proportional, derivative, and integral controllers adjust outputs continuously based on error, rate of change, or accumulated error, rather than jumping between two fixed limits with a deadband.