Achieve high-precision, highly responsive, and stable linear motion control; keep following error within the micrometer range; and eliminate vibration and abnormal noise.
Precision requirement: ±0.5 μm; Key stages: 6 major phases; Core challenge: Vibration suppression.
1. Pre-commissioning Preparation and Hardware Connection
Thorough preparation before powering up helps avoid most basic errors and ensures safe, efficient commissioning.
1.1 Mechanical and Electrical Checks
Verify that the linear motor guideway meets standards for parallelism and flatness, and ensure the forcer (slider) moves smoothly without binding. Check that all power cables (U/V/W), encoder cables, and power supply lines are securely connected, and ensure reliable single-point grounding of shields to prevent noise caused by ground loops.
1.2 Key Parameter Confirmation
Record the rated thrust, continuous thrust, peak thrust, back-EMF constant (Ke), phase resistance (R), inductance (L), and encoder resolution from the motor manual. For high-precision applications, an external linear scale must be used to establish a fully closed-loop system, compensating for errors such as mechanical thermal deformation.
1.3 Software Connection
Connect the drive to the commissioning PC using a Gigabit Ethernet cable and install the appropriate commissioning software (e.g., Googol's commissioning software or Servotronix's ServoManager) to ensure a successful communication link.
2. Basic Parameter Configuration and Motor Identification
The goal of this stage is to enable the drive to "recognize" and initially control the motor, establishing a proper control foundation.
| Step | Operation | Key Parameters / Objective |
|---|---|---|
| 1. Enter Motor and Encoder Parameters | Manually enter the motor’s rated parameters, encoder type, and encoder resolution in the software. | Ensure that the electrical angle correctly corresponds to the mechanical angle. |
| 2. Set the Control Mode and Feedback Source | Set the control mode, such as position mode P0.01=2, select the command source, and enable the external linear encoder as the primary position feedback. | P14.01=1 enables external feedback and prevents the linear encoder signal from being ignored. |
| 3. Set the Electronic Gear Ratio | Calculate and set the electronic gear ratio according to the linear encoder resolution and the required pulse equivalent. | Example: P3.01=1000 and P3.02=1, so 1,000 pulses correspond to 1 mm of travel. |
| 4. Perform Motor Parameter Auto-Tuning | Run the drive’s static identification function to automatically measure motor resistance, inductance, and other parameters. | Obtain accurate Ke, R, and L values to optimize FOC control and decoupling performance. |
| 5. Perform Phase Search and Direction Testing | Perform a low-speed phase search to confirm the correct UVW phase sequence. Send a small pulse command to test the direction of motion. | An incorrect direction can be corrected by swapping the U and V phase wires or changing the direction parameter, such as P1.10=1. |
3. Control Loop Commissioning and Gain Tuning
This is the core of the commissioning process, aimed at optimizing the system's dynamic response performance and balancing speed with stability.
Three-Loop Commissioning Sequence and Essentials
3.1 Current Loop Commissioning
Monitor Id (excitation current command) and Idr (feedback); adjust gains so the two curves track closely with a phase lag of approximately 0.4 ms, ensuring fast and accurate current control.
3.2 Motor Inertia Identification
Command the motor to move back and forth at a specific speed to bring the current close to the rated value, allowing the drive to automatically calculate the total mass and inertia ratio. Reduce speed/position loop gains after completion.
3.3 Speed Loop and Position Loop Tuning
Follow the "loose-to-tight" principle: start with a lower proportional gain for the speed loop (e.g., 30–50), gradually increase it until slight ringing appears, then back it off by 10%–20%. The position loop proportional gain is typically set to one-quarter of the speed loop gain.
During tuning, use the software oscilloscope function to monitor key curves: position following error (Perr), commanded velocity (Vcmd), feedback velocity (Vfd), commanded current (Icmd), and feedback current (Ifb). The goal is to stabilize the following error within the target range (e.g., ±0.5 μm) during the constant-speed phase and ensure the current curve is smooth without oscillation.
4. Vibration Analysis and Filter Application
Mechanical resonance is a common, persistent issue in linear motor systems that requires precise "diagnosis" and "treatment" via frequency response analysis.
4.1 Diagnostic Tools
Use the FFT (Fast Fourier Transform) tool in the tuning software to analyze the Icmd and Ifb current curves. Spikes at specific frequencies indicate the presence of mechanical resonance.
4.2 Treatment Methods
Apply a notch filter (band-stop filter) to the speed loop output filter. Set the center frequency to the resonance frequency and adjust the bandwidth and depth to suppress vibration.
4.3 Filter Configuration Example
If the resonance frequency is 300 Hz, settings could be: P5.30=1 (enable), P5.31=300 (center frequency), P5.32=50 (bandwidth), and P5.33=10 (attenuation depth).
Note: Avoid using too many notch filters; one or two are usually sufficient. Excessive use introduces phase lag, which affects system response.
5. Advanced Optimization and Performance Verification
Once the basic loops are stable, fine-tuning and comprehensive testing are required to ensure reliable system operation under various conditions.
5.1 Feedforward Compensation
To reduce position following error during acceleration and deceleration, apply acceleration feedforward gain. This significantly improves dynamic response and reduces lag.
5.2 Performance Verification Checklist
- Following Error Test
In full closed-loop mode, the error during the constant-speed phase should stabilize within ±3–5 pulses.
- Repeatability Test
After multiple round trips to the same position, the deviation should be less than ±1 μm.
- Temperature Rise and Load Testing
Monitor the motor's temperature rise during prolonged operation. Refer to the continuous thrust curve in the motor manual to avoid overheating caused by exceeding rated values.
- Safety Function Testing
Verify that functions such as hardware limits, software limits, and encoder wire-break detection trigger correctly.
6. Commissioning Precautions
- Wiring Standards
Power cables, encoder cables, and communication lines must be routed separately, keeping them well away from strong interference sources like variable frequency drives (VFDs) and welding machines. Ensure cable shields are grounded at a single point.
- Mechanical Resonance
Abnormal vibration or high-pitched noise during commissioning is often caused by mechanical resonance. Use FFT analysis to identify resonance points and suppress them using notch filters.
- Parameter Backup
Back up all tuned parameters to ensure quick restoration during equipment maintenance or replacement.
- Seeking Support
For complex mechanical resonance issues or advanced function commissioning, contacting the drive supplier's technical support is the most efficient way to resolve problems.
Key Principles
Understand the system and proceed step-by-step. Success in linear motor commissioning relies 30% on the hardware and 70% on the tuning process. Unlike rotary servos, which benefit from the buffering effect of a gearbox, linear motors directly amplify any parameter errors or mechanical defects. Remember this principle: first ensure safe operation, then aim for smooth movement, and finally optimize accuracy and response. Never blindly increase feed-forward or gains before the basic control loops are stable. Linear motor performance depends on the synergy between the mechanical foundation, sensor accuracy, and control algorithm tuning.