SANMOTION PB servo stepper

SANYO DENKI Communication Servo New Benchmark: SANMOTION PB Series

In the field of industrial automation, there has long been a trade-off between performance and cost between stepper systems and servo systems. Although open-loop stepper systems have low cost and high low-speed torque, they have disadvantages such as out of step, high heat generation, and limited positioning accuracy; The communication servo system has excellent performance, but the price is high and the control is complex. The "SANMOTION Model No. PB" series launched by Sanyo Denki in Japan was born to fill this market gap. This series of products was initially applied to positioning equipment in conveyor systems, as well as short stroke, high-frequency action scenarios that utilize the low-speed and high torque characteristics of stepper motors. In recent years, with the increasing speed and reliability of stepper systems, as well as the demand for servo system replacements, the market's demand for high torque, cost-effective, and high-performance solutions has been growing. In this context, Sanyo Electric has developed the "SANMOTION Model No. PB" series of new products with AC power input. This article will comprehensively analyze product architecture, technical specifications, core innovations, and user functions.

Product architecture and system composition

The SANMOTION PB series consists of an amplifier (driver) and a stepper motor, using closed-loop control technology that combines the advantages of stepper motors and servo drives.

1. Amplifier (driver)

The external dimensions of the amplifier are 150 mm high, 42 mm wide, and 120 mm deep, with a weight of approximately 0.64 kg. It adopts a tray type structure, which is easy to install in the control cabinet. Power input support:

Single phase AC 100/115 V

Single phase or three-phase AC 200/230 V (allowable voltage fluctuation+10%/-15%)

The amplifier interface is divided into four types, combining pulse chain input with RS-485/parallel I/O (point controlled, programmable type, referred to as R-type). The specific models are PB4A002R30 * (RS-485/parallel I/O interface) and PB4A002P30 * (pulse chain input interface). The driving method is sine wave PWM control.

2. Motor series

There are 5 types of motors, covering three machine base sizes: 42mm square, 60mm square, and 86mm square. The same amplifier can drive all motors, achieving flexible power matching. The basic parameters of the motor are as follows:

Motor model, machine base size, maximum holding torque (N · m), rotor inertia (kg · cm ²), allowable axial load (N), allowable radial load (N), mass (kg)

PBM423FXK20 42 mm 0.39 0.056 9.8 49 0.35

PBM603FXK20 60 mm 1.3 0.4 14.7 167 0.85

PBM604FXK20 60 mm 1.9 0.84 14.7 167 1.42

PBM861FXK20 86 mm 3.5 1.48 60 200 1.9

PBM862FXK20 86 mm 6.6 3.0 60 200 3.1

The motor is equipped with an optical incremental encoder as standard, with a resolution of 4000 P/R (A/B/C phase, with phase origin signal), and can reach 16000 P/R after four harmonics, providing a hardware foundation for high-precision positioning.

Optional accessories include:

Maintain the brake (applicable to 42 mm and 60 mm motors)

Low backlash gear (suitable for 42 mm and 60 mm motors)

Harmonic gear (applicable to 42 mm and 60 mm motors)

Detailed specifications of amplifier

The main technical parameters of the amplifier are as follows:

Positioning resolution: up to 3200 P/R (can be set through electronic gear function)

rotation speed

42mm and 60mm motors: 0~4500 min ⁻¹

86mm motor: 0~4000 min ⁻¹

Speed command resolution: 1 min ⁻¹

Built in features:

Maintain brake control function

Regeneration control function (no external regeneration unit required)

Point control function, program function

Teaching function

Operation function:

Positioning, jog, origin reset, forced operation

Module length function

Digital operator: parameter setting, motor combination, resolution setting, jog, teaching, etc

Protection function:

Motor overheating, amplifier overheating, abnormal power supply voltage

Sensor disconnection, overspeed, RST action, CPU error, EEPROM error

PAM voltage error, overload error, overcurrent detection

The input and output signals are very rich:

Input signal:

Universal input: 8 points (selectable point/program number selection, execution, origin, limit, pause, stop, interlock, jog, deviation reset, counter reset, brake control, etc.)

Pulse input: 1 or 2 channels

Dedicated inputs: positive/negative limit, emergency stop, alarm clearing

Universal input (communication type): 2-point (deviation reset, forced, current selection, brake control, counter reset, etc.)

Output signal:

alarm output

Universal output: 7 points (positioning completed, busy, response, ZONE, point number, push end, origin end, etc.)

Positioning completed, ready, encoder signal (phases A/B/C)

Universal output (communication type): 2-point (origin end, push end, ZONE, input monitoring, pulse input, etc.)

All input/output signal functions and logic can be set through communication, with extremely high flexibility.

Core technology innovation

1. The motor's heating is significantly reduced

The traditional open-loop stepper system adopts constant current drive, and regardless of the load size, the motor always flows through the rated current, resulting in severe heating. The PB series adopts proportional integral control, which only provides necessary current based on the operating status of the load, thereby reducing heat generation. However, although PB products with early communication input had fast current response, the current ripple caused by PWM control was large, resulting in iron loss of multipole stepper motors becoming the main cause of heating. The newly developed communication input PB series adopts innovative control methods to significantly reduce current ripple without compromising responsiveness. Taking the 42mm motor as an example, the motor heating during stop is reduced by about 80% compared to traditional products. Comparison of current waveforms shows that the new product has a smoother current waveform and significantly reduced ripple amplitude.

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:

Conveyor system positioning: such as pallet positioning for electronic assembly lines and packaging machinery.

Short stroke high-frequency actions: such as dispensing machines, surface mount machines, and stamping feeders.

Vertical axis load: using a holding brake to prevent falling, combined with closed-loop control to ensure the accuracy of the stopping position.

Alternative servo system: In applications that require high torque but are budget sensitive, the PB series provides a cost advantage close to servo performance.

Label equipment and printing machinery: The improved command synchronization and deviation reset function meet the high-precision intermittent feeding requirements.

When selecting, it is necessary to consider:

Required torque and speed: Refer to the motor speed torque curve.

Load inertia ratio: Ensure system stability, use electronic gears or adjust gains if necessary.

Do you need to maintain the brake: When maintaining the position of the vertical axis or when power is off, choose a motor with a brake.

Interface type: Pulse chain input suitable for traditional motion controllers; RS-485/parallel I/O and R-type programmable are suitable for independent operation or distributed systems.