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Easy Servo Products
(Closed Loop Steppers)
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Highlights
- Step & direction, or CW/CCW control
- Stepper based servo control
- Fully closed position loop
- Never stall or lose of steps
- Always 100% implementation of available torque
- Load-based output current from servo drive to motor
- High starting torque and quick response
- No overshooting and zero settling time
- Extra low motor heating, smooth motor movement
- No tuning for plug & play
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OverviewMain Features
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By adopting high resolution encoders, Leadshine ES series easy servo systems apply servo controls on traditional steppers. It was uniquely designed to take the advantages from both traditional brushless servo systems and conventional stepper systems. While inheriting the features of high starting and high stiffness from stepper systems, position loops between easy servo motors and drives are fully closed in real time. Therefore, loss of movement synchronization is totally eliminated. Compared with brushless servo systems, Leadshine easy servo have advantages in much higher low-to-middle speed torque, much lower cost, quicker response, zero setting time, no tuning...
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Traditional stepper systems operate in open-loop modes to provide position control. They are simple to implement and are cost effective. In an open-loop system, a stepper drive sends commands to move the driven stepper motor. It does not know where is the "Current" motor shaft position, due to the lack of feedback. It keeps sending commands and tries to move the load attached to the stepper motor, to targeted position. But in open-loop mode, because of sudden load changes, potential loss of motor movement synchronization between commanded position and actual positions can happen and result in "Loss of Steps" or even motor movement "Stall". This can be fail the whole control system, damage the processed materials, or even crush the whole applications.
In the past, engineers are forced to choose servo systems to avoid the above problem of open-loop stepper systems. Servo systems are very expensive and hard to setup. In many brushless servo systems, it is common that an engineer has to configure tens or even hundreds of parameters to get the performance they need. In many applications, best tuned expense high-end brushless servo systems can't outperform quality open-loop stepper systems (in the condition of no stall or loss of steps). Brushless servo systems are lack of high torque feature of stepper motors. In many cases, expensive planetary gearboxes have to be added to achieve desired torque. Other issues like hunting (shaking in motor movement), overshooting, long setting time..., are also commonly seen in servo systems, but not in open-loop stepper systems.
By adopting high resolution encoders to update stepper motor shaft position real-time, Leadshine ES series easy servo systems combine open-loop stepper and servo technologies together. They naturally inherit advantages of both stepper and servo systems. ES series easy servo systems feature high position accuracy, real-time motor movement synchronization, low cost, high torque, no tuning, high stiffness, no tuning, zero settling time, low motor heating, smooth motor movement, no hunting, no overshooting, zero settling time.... All those features make Leadshine hybrid servo systems ideal choices for many OEM applications.
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In open-loop stepper systems, potential loss of motor movement synchronization limits their adoption for many applications. Engineers are forced to reserve 50% of available stepper motor torque to avoid possible loss of steps. With the adoption of high resolution encoders to feedback real time motor shaft positions, Leadshine ES series easy servo drives close the position loops between servo drives and driven motors. That will keep motor movement synchronized all the time, and allow 100% of available torque.
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Due to closed loop control and adoption of advanced control algorithm, ES series easy systems can always implement 100% torque of the motor, and do not need the huge 50% torque reservation in normal open-loop stepper systems. This feature significantly improves system high speed performance. While open-loop stepper systems are typically adopted in applications under 1,000 rpm, ES series easy servo systems are ideal for many applications up to 2,000 RPM; sometimes even for 3,000 RPM!
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In open-loop stepper systems, output current to the stepper motor from the step driver is constant. No matter what load condition is and how much current is needed, the stepper driver will always input a constant current.
With the position loop closed in ES series easy servo systems, output current from the servo drive to the driven motor is load based. The servo drive will only input just-enough current to the driven motor to move the attached load. This can significantly lower the drive and motor heating.
Compared with open loop systems, motor heating of in ES series easy servo systems can be reduced for 20-40°C.Thus, life time in ES series easy servo systems is much longer, power consumption is lower, and maintenance costs will also be reduced.
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Unlike conventional stepper systems, ES series easy servo systems adopt vector control algorithm, same as brushless servo controls. Input commands are filtered for smooth motion with minimum torque ripples. Therefore, resonance in open-loop stepper systems is significantly minimized, and motor movement noise of can be significantly reduced, up to 70%.
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In a traditional brushless servo system, there is a considerable delay for the servo motor to response ("move") to a command signal sent from a motion controller or PLC. This delay is caused by servo "settling time".
Leadshine ES series easy servo systems adopt servo control for stepper motors. Motor movement is always synchronized with input pulse commands. When receiving a pulse signal, an ES servo drive will response immediately and start motor movement. When it finishes execution of the input pulses, it stops immediately without any movement fluctuation. So, there is no hunting ("shaking") or overshooting, which is commonly seen in traditional brushless servo systems.
This feature, "Quick Response, No Hunting, No Overshooting, and Zero Settling Time", makes ES easy servo systems ideal for short-distance applications requiring rapid motion, such as bonding and vision type systems.
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For traditional brushless servo systems, in order to get the preferred performance, an engineer has to spend hours even days, to tune servo gains which involves tens or even hundreds of servo parameter configurations. But there is no such gain for ES series easy servo systems. They are designed for simple setup, "no tuning, plug and play", with all configurations are already optimized.
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Compared with traditional brushless servo systems, Leadshine ES series easy servo systems offer much higher start and low speed torque, due to the natural inheritance of high stiffness at standstill and high starting torque feature from stepper systems. This allows ES easy servo systems to perform direct drive of high inertia load, like flywheels and belt driving. But in traditional brushless servo systems, in order to get the preferred torque, expensive high power servo motors have to be chosen, or costly planetary gearboxes have to be added in many applications. While load inertia ratio normally can't exceed 10:1 in traditional brushless servo systems, that ratio can be as high as 100:1 in ES easy servo systems.
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Easy Servo Motors |
(click for details) |
- NEMA 23 to 42 frame size
- Holding torque of 128 - 2,832 oz-in (0.9 to 20 N.m)
- Integrated 1,000-line encoders, higher resolution optional
- High precision
- Extra low motor heating
- Smooth motor movement
- Widely implemented in OEM applications
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Easy Servo Drives |
(click for details) |
- Stepper based servo control
- Step & direction or CW/CCW control
- Closed position loop for servo control without lose of steps
- No torque reservation for driven motors
- Max 100VDC/80VAC, or direct 120/230 VAC input
- Load-based output current for much lower motor heating
- Smooth and quiet motor movement
- Quick response time and zero settling time
- No hunting and no overshooting when compared servo systems
- Much lower motor/drive heating than open-loop stepper systems
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