The peripheral motion control system of an industrial robot mainly consists of three key components: servo control, step control, and frequency conversion control. Each of these plays a crucial role in ensuring precise and efficient movement. Let’s explore each one in detail.
**Servo Control**
**1. Working Principle of AC Servo Motor**
An AC servo motor features a rotor made of a permanent magnet. The stator, consisting of U/V/W three-phase windings, generates an electromagnetic field when powered by the driver. This magnetic field causes the rotor to rotate. The motor's encoder provides feedback to the driver, which compares the actual position with the target value and adjusts the rotor angle accordingly. The accuracy of the motor is directly dependent on the resolution (number of lines) of the encoder.
**2. Composition and Classification of the Servo System**
A servo system is a control system that manages position, angle, speed, angular velocity, acceleration, and force. These systems can be classified based on control structure and drive components:
- **Control Structure**: Open-loop or closed-loop.
- **Drive Components**: Stepper motor, DC motor, or AC motor-based systems.
**3. Characteristics of AC Servo Motors**
- High positioning accuracy (up to 0.036 degrees).
- Fast response time.
- Flexible and easy-to-implement control.
- Wide range of models available for different applications.
- Full closed-loop control ensures real-time monitoring and adjustments.
**4. Servo System Structure**
[Image: A diagram illustrating the components of a servo system.]
**5. Servo Control Selection Steps**
- Determine mechanical specifications such as load, stiffness, and inertia.
- Confirm motion parameters like speed, stroke, and acceleration.
- Select motor inertia, load inertia, and rotor inertia.
- Choose the appropriate motor speed and rated torque.
- Decide on the motor's mechanical position resolution.
- Finally, select the motor model based on all the above factors.
**6. Applications of Servo Control**
[Image: Examples of servo control in industrial applications.]
**Step Control**
**1. Working Principle of Stepper Motor**
A stepper motor converts electrical pulses into angular displacement. When it receives a pulse, it rotates a fixed angle (step angle) in a set direction. By controlling the number of pulses, the motor can achieve accurate positioning. Pulse frequency controls speed and acceleration, making it ideal for open-loop control systems with no error accumulation.
**2. Classification of Stepper Motors**
Common types include:
- **Reactive Stepper Motors (VR)**: Three-phase, large torque, but noisy.
- **Permanent Magnet Stepper Motors (PM)**: Two-phase, small torque, larger step angles.
- **Hybrid Stepper Motors (HB)**: Combines PM and VR advantages, widely used due to high precision (e.g., 1.8° or 0.72°).
**3. Stepper Motor System**
[Image: A schematic of a stepper motor system.]
**4. Key Parameters of Stepper Motors**
- Step angle, phase number, beats, static torque, and dynamic characteristics like step angle accuracy and maximum no-load frequency.
**5. Selection Criteria for Stepper Motors**
- Step angle based on required precision.
- Static torque based on load requirements.
- Current selection using torque-frequency curves.
**6. Performance Comparison with Servo Motors**
- Servo motors offer higher accuracy, smoother low-speed operation, and better overload capability.
- Stepper motors are cost-effective but lack closed-loop feedback and have limited speed performance.
**Frequency Control**
**1. Introduction to General Motors**
The most common type of induction motor is the three-phase squirrel-cage AC motor. It is known for its simplicity, reliability, and wide application in industrial settings.
**2. Principle and Composition of the Inverter**
An inverter is a device that adjusts the speed of an AC motor by changing the power supply frequency. Its main components include:
- **Rectifier**: Converts AC to DC.
- **DC Link**: Smoothes the DC voltage.
- **Inverter**: Converts DC back to AC at the desired frequency.
- **Brake Circuit**: Manages regenerative energy during braking.
**3. Application of Inverters**
Inverters are used in adjustable speed drives to control motor speed efficiently. They are essential in applications requiring variable speed, energy savings, and precise control.
[Image: A diagram showing the components of an inverter.]
In summary, each control method has its own strengths and weaknesses. Choosing the right system depends on the specific application requirements, budget, and performance expectations. Whether it's the precision of servo control, the simplicity of step control, or the versatility of frequency control, understanding their differences helps in making informed decisions in industrial automation.
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