Actuators and Drive Selection
An actuator converts electrical, pneumatic, hydraulic, or thermal energy into motion or force. Drive selection is the bridge between the control signal and the real mechanical load.
Learning Objectives
By the end of this lesson, you should be able to:
- compare DC motors, steppers, servos, solenoids, and linear actuators;
- match actuator type to load, speed, precision, and duty cycle;
- choose driver voltage and current ratings;
- include protection, feedback, and thermal limits;
- identify unsafe actuator-control assumptions.
Actuator Types
| Actuator | Strength | Limitation |
|---|---|---|
| DC motor | simple speed control, good power density | needs feedback for position |
| Stepper motor | open-loop positioning at low speed | can miss steps, loses torque at speed |
| Servo motor | closed-loop control built in or external | cost and tuning complexity |
| Solenoid | fast short-stroke motion | heat and high inrush current |
| Linear actuator | integrated linear motion | slower, mechanical limits |
Drive Selection Flow
Driver Ratings
Check continuous current, peak current, voltage range, thermal resistance, switching method, braking behavior, and protection features. A driver rated for 2 A peak may not survive 2 A continuous without heatsinking.
For motor drives, current often sets torque while voltage helps reach speed by overcoming winding inductance and back EMF.
Protection
Actuators are energy devices. Practical systems need flyback paths, fuses or current limits, thermal shutdown, limit switches, emergency-stop behavior appropriate to the hazard, and a safe startup state.
Common Mistakes
- Choosing an actuator before calculating load torque.
- Ignoring inrush or stall current.
- Driving inductive loads without clamps.
- Assuming open-loop steppers never lose position.
- Forgetting mechanical end stops and fault recovery.
Summary
Actuator selection starts with the load and motion profile, not the controller. Choose the actuator, transmission, driver, supply, protection, and feedback as one system.
Further Reading
- Pololu, Maxon, and Oriental Motor application guides.
- Texas Instruments motor-driver selection resources.
- IEC 60204-1 machinery electrical safety concepts.