Introduction
Servo motors are the core actuators in robotics projects, directly impacting system stability, precision, and response speed. This article will analyze how to scientifically select servo motors based on five technical dimensions: torque, speed, power supply, control interface, and feedback mechanisms.
1. Torque: The Foundation of Power Requirements
- Stall Torque vs. Operating Torque: Stall torque is the maximum output before motor stalling, while operating torque must be calculated based on actual loads.
- Calculation Formula: The torque for robotic arm joints must consider leverage effects (
τ = F × r), while wheeled robots require calculations for hub driving torque. - Safety Margin: It is recommended to select a motor with torque at least 1.5 times the theoretical requirement to avoid overload.
2. Speed and Gear Ratio: Balancing Speed and Power
- No-Load Speed: The maximum speed without load, but actual speed decreases under load.
- Gear Reduction: High reduction ratios (e.g., 1:100) increase torque but reduce speed, suitable for lifting robots; low ratios (e.g., 1:10) are ideal for high-speed applications (e.g., drone servos).
3. Power Supply Design: Matching Voltage and Current
- Voltage Levels: Common options include 6V, 12V, and 24V. Higher voltage yields greater power output (
P = V × I) at the same current. - Peak Current: High-torque motors may trigger power supply protection during startup, requiring compatible power modules.
4. Control Interface: Analog vs. Digital
- PWM Analog Signal: Low cost and compatible with entry-level controllers like Arduino, but limited precision (typically 0.5°–1° error).
- Digital Communication (UART/CAN): Models like Dynamixel support serial commands, achieving 0.1° precision, ideal for multi-axis coordination.
5. Feedback Systems: Open-Loop vs. Closed-Loop
- Potentiometer: Low-cost but prone to wear, with degrading precision over time.
- Optical Encoder: High resolution (12-bit = 4096 steps/revolution), long lifespan, suitable for precise positioning.
Conclusion
Technical parameter selection must be based on quantified requirements of the actual application. Simulation tools (e.g., MATLAB Simulink) or prototype testing are recommended to validate motor performance and avoid theoretical deviations.
