SANMOTION PB servo stepper

2. Torque Enhancement and Low Power Consumption

Traditional products have to use voltage reduction circuits to limit the voltage applied to the motor due to the motor heating problem in PWM systems, resulting in a decrease in current time constant and insufficient torque during high-speed operation. The new product eliminates the voltage reduction circuit by improving the PWM control system (reducing current ripple), while optimizing the motor winding specifications and improving motor efficiency, thereby achieving high torque and low power consumption. Taking the 86 mm square motor (PBM862) as an example, the speed torque characteristic curve shows that the torque output of the new product is significantly higher than that of traditional products throughout the entire speed range (especially in the high-speed zone), while the current consumption is lower. Cancelling the voltage reduction circuit also reduces the number of components and improves reliability.

3. Significant improvement in positioning accuracy (anti load interference)

Traditional stepper motors typically utilize self holding torque when stopped, switching from closed-loop control to open-loop control to completely stop the motor. But under open-loop control, when there is an unbalanced load, the motor will produce angular deviation, which will damage the positioning accuracy (such as vertical axis load falling). Although closed-loop control (servo locking) can always be maintained, it can cause small vibrations and lose the advantage of complete stillness. To solve this contradiction, the new product significantly increases the encoder resolution from the traditional 500 P/R to 4000 P/R (16000 P/R after four harmonics), which can detect extremely small positional deviations when stopped. At the same time, through the unique position compensation function, high positioning accuracy independent of load conditions has been achieved while maintaining the advantage of complete stillness, especially improving the accuracy of repeated positioning. Figure 5 (original schematic diagram) shows the improvement effect of position error under unbalanced load.

4. Improvement of instruction synchronization

Proportional integral control has the advantages of avoiding step loss and suppressing speed fluctuations caused by resonance in stepper systems, but its disadvantage is that it can damage command synchronization, that is, there is a positional deviation (tracking error) between the command position and the actual position. In some applications, such as tag devices, this deviation is unacceptable. The new product significantly reduces position deviation in pulse chain input products by adding a feedforward (FF) function to the position loop. At the same time, for devices that require external signals to clear position deviations (such as intermittent label machines), the new product enhances the deviation reset operation mode, making devices that were previously difficult to apply the PB series applicable now. Figure 6 shows the comparison of operating waveforms with and without feedforward function: with FF function, the command almost coincides with the actual position.

User friendly features

In addition to the core performance improvements mentioned above, the PB series also comes with multiple built-in features that are easy to use and maintain:

Digital operator: As a standard configuration, it can easily set various parameters and perform test runs without the need to connect to an upper computer.

Teaching function: R-type (programmable) can independently achieve online/offline teaching through digital operators, simplifying debugging.

7-segment LED display: Clear display of alarm content and amplifier status for easy fault diagnosis.

Maintain brake control: The amplifier has built-in control logic and does not require external brake power or relay contacts. It can be directly connected to the motor with the brake.

Regeneration control function: Equipped with a unique regeneration control circuit, it does not require an external regeneration resistor unit, saving space and cost.

Forced operation function: Even pulse input types come standard with a forced operation function, which allows for easy power on debugging of pneumatic equipment.

System connection and wiring

The external wiring of the amplifier (taking AC 200 V input as an example) includes the main circuit power supply, control power supply, motor power line, encoder signal line, I/O signal line, and communication interface. Please note:

The main circuit power supply and control power supply can be independently powered, making it easy to keep the control circuit energized during emergency stops.

Pulse input type supports 1 or 2 pulses (CW/CCW or pulse+direction), with the highest input frequency not specified but capable of high-speed positioning.

The RS-485 interface supports half duplex communication and can be used for networking multiple devices, with the help of R-type programmable functions to achieve distributed control.

Application Fields and Selection Suggestions

The SANMOTION PB series is suitable for the following typical scenarios: