Harmonic actuator
Harmonic Drive LPA low-profile actuator with integrated servo drive
A flat rotary actuator with zero-backlash strain wave gearing, a motor, dual absolute encoders and a 48 VDC servo drive built into one unit. It is controlled over CANopen or EtherCAT.
Key specifications
| Rated torque (max) | 16.9 Nm |
|---|---|
| Peak torque (max) | 57 Nm |
| Speed (max) | 88.2 rpm |
| Supply | 48 VDC nominal (24–60 VDC) |
| Ratio | 51–101:1 |
| Backlash (max) | 0 arcmin |
| Sizes | 20 |
Summarised in our own words from Harmonic Drive SE / Harmonic Drive LLC's published data; series maxima, individual models vary. Last checked 2026-10-29. Source 1
Notes on this data
Only LPA-20 is published, with ratios 51, 81 and 101. Peak torque is 34/49/57 Nm and rated 6.5/16 (ratio 81)/16.9 Nm. Maximum speed is 88.2/55.6/44.6 rpm. Communication is CANopen (DS301/DS402) or EtherCAT. Encoders are 15-bit on the motor and 14-bit on the output, both absolute. The unit is for indoor use only at 0–40 °C; no IP rating is given.
Specify Motion is not affiliated with Harmonic Drive SE / Harmonic Drive LLC. Harmonic Drive and LPA low-profile actuator with integrated servo drive are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a Harmonic Drive part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These 3 series from our supply network are the closest match on published figures.
Hollow-shaft harmonic servo actuator: strain-wave gearing, motor, encoder and brake in one unit, run from a separate servo drive. Six frame sizes, from 48 VDC to 220 VAC.
| Published maximum | LPA low-profile actuator with integrated servo drive | MAH |
|---|---|---|
| Peak torque | 57 Nm | 800 Nm meets or exceeds |
| Rated torque | 16.9 Nm | 557 Nm meets or exceeds |
| Speed | 88.2 rpm | 125 rpm meets or exceeds |
Large-bore version of the harmonic actuator with a frameless 16-pole motor, giving a much bigger through-hole for cabling. Two sizes.
| Published maximum | LPA low-profile actuator with integrated servo drive | MAT |
|---|---|---|
| Peak torque | 57 Nm | 800 Nm meets or exceeds |
| Rated torque | 16.9 Nm | 557 Nm meets or exceeds |
| Speed | 88.2 rpm | 102 rpm meets or exceeds |
Harmonic actuator with an integrated German-made Synapticon Circulo servo drive on EtherCAT, with STO and optional FSoE functional safety.
| Published maximum | LPA low-profile actuator with integrated servo drive | MGM |
|---|---|---|
| Peak torque | 57 Nm | 459 Nm meets or exceeds |
| Rated torque | 16.9 Nm | 267 Nm meets or exceeds |
| Speed | 88.2 rpm | 108 rpm meets or exceeds |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
What a harmonic actuator is
A harmonic actuator is a rotary servo actuator that combines a strain-wave gear, a servo motor, a position encoder and often a brake in one compact housing. Many have a hollow shaft for cables, and some include the servo drive with a fieldbus interface. The strain-wave gear gives a high ratio with near-zero backlash, while a precision output bearing carries the load directly. The actuator is ready to mount as a robot joint or precision rotary axis.
When engineers choose a harmonic actuator
Choose a harmonic actuator for robot joints, positioners and precision rotary axes where compact size, zero backlash and fast integration matter. It saves the design effort of combining motor, gear, encoder and bearings. The trade-offs are cost and flexibility: the motor, gear ratio and feedback are fixed by the range, and torque limits are set by the strain-wave gear. For heavy shock loads, a cycloidal solution may be more robust.
How to specify the Harmonic Drive LPA low-profile actuator with integrated servo drive
Send these with your enquiry and an engineer can confirm the right LPA low-profile actuator with integrated servo drive variant or an equivalent:
- Rated and peak output torque (Nm)
- Output speed (rpm)
- Ratio (:1)
- Hollow shaft diameter (mm)
- Feedback: motor-side and output-side encoders
- Brake and integrated drive options
- Supply voltage and interface
Common mistakes to avoid
- Exceeding momentary torque in a collision
- Ignoring output bearing moment load
- Mismatching drive and encoder interface
- Forgetting heat in continuous duty
Harmonic Drive LPA low-profile actuator with integrated servo drive: frequently asked questions
What is the Harmonic Drive LPA low-profile actuator with integrated servo drive?
A flat rotary actuator with zero-backlash strain wave gearing, a motor, dual absolute encoders and a 48 VDC servo drive built into one unit. It is controlled over CANopen or EtherCAT. Published series figures include rated torque 16.9 Nm, peak torque 57 Nm, speed 88.2 rpm, ratio 51:1. It is made by Harmonic Drive SE / Harmonic Drive LLC; Specify Motion can help source it or propose an equivalent.
Who makes the Harmonic Drive LPA low-profile actuator with integrated servo drive?
The Harmonic Drive LPA low-profile actuator with integrated servo drive is made by Harmonic Drive (Harmonic Drive SE / Harmonic Drive LLC) and is listed here for engineers comparing options. Specify Motion is not affiliated with Harmonic Drive SE / Harmonic Drive LLC; brand names are used only to identify the product.
What is the rated torque of the Harmonic Drive LPA low-profile actuator with integrated servo drive?
The published series maximum rated torque is 16.9 Nm. Individual models and sizes in the LPA low-profile actuator with integrated servo drive range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Harmonic Drive LPA low-profile actuator with integrated servo drive?
Yes. On published figures, MAH and MAT are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
What is the benefit of dual encoders on a harmonic actuator?
A motor-side encoder controls the motor, while an output-side encoder measures the joint position directly after the gear. This compensates for gear deflection and gives true absolute output position at power-up. Dual encoders improve accuracy and support safety and collision detection.
Can a harmonic actuator include its own drive?
Yes, some versions integrate the servo drive and communicate over EtherCAT, CANopen or similar networks. This reduces cabinet space and wiring. Other versions connect to a separate servo drive. Choose by machine architecture, cabinet space and the safety functions needed, such as safe torque off or functional safety over the network.
Further reading: How to select a harmonic actuator · Harmonic vs planetary vs cycloidal · Gearboxes and harmonic drives
Other harmonic actuator series
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