Direct engineering answer: choose a documented model, not a gear-family promise
Compare harmonic and planetary reducers using required output torque and speed, lost motion, stiffness, thermal limits, load spectrum and installation space. A reducer type does not guarantee a fixed efficiency, lifetime or impact tolerance. For complete ZHR actuators, select the model and ratio first, then verify the corresponding specifications and interface.
Published family screening ranges: ZHR-H rated torque: 5-91 Nm by model and reduction ratio; peak torque: 15-210 Nm. ZHR-P rated torque: 1.6-40 Nm by model; peak torque: 5.5-120 Nm. These are family boundaries, not a sizing result.
Updated September 18, 2026. The values below reproduce the site's reviewed product facts; they are family screening ranges, not a guarantee for every configuration.
1. Separate the mechanism from the actuator specification
A harmonic or strain-wave reducer uses a wave generator to deform a flexible gear into engagement with a surrounding gear. A planetary reducer uses gears rotating around a central gear within a ring gear. The specific ratio, materials, bearings and design determine the operating limits.
A complete joint module also includes a motor, sensing, structure and potentially a drive. Compare complete actuator outputs with complete actuator outputs; reducer-only efficiency and motor-only torque density cannot stand in for system performance.
2. Published ZHR-H and ZHR-P screening ranges
| Family | Rated output torque | Peak output torque | Interface boundary |
|---|---|---|---|
| ZHR-H harmonic | 5–91 Nm by model and ratio | 15–210 Nm by model and ratio | CAN / RS485; confirm exact configuration |
| ZHR-P planetary | 1.6–40 Nm by model | 5.5–120 Nm by model | Model-specific; P60 is CAN only without native EtherCAT |
Sources: ZHR-H specifications and ZHR-P specifications. Do not combine one configuration's maximum torque with another configuration's speed or mass. Peak duration and thermal conditions still require confirmation.
3. Compare the evidence needed for your application
| Requirement | Request for each exact model | Avoid assuming |
|---|---|---|
| Positioning | Lost-motion test, stiffness, repeatability and measurement conditions | Encoder resolution equals joint accuracy or zero backlash |
| Energy use | Efficiency over the intended torque-speed cycle | A single efficiency number predicts battery runtime |
| Dynamic contact | Permissible peak load, duration, bearing moment and repeated-load limits | Peak motor torque proves impact survival |
| Backdriving | Backdrive torque under defined operating conditions | Every planetary module is a QDD or inherently backdrivable |
| Service life | Load spectrum, maintenance conditions and supporting test evidence | A gear family guarantees a fixed number of hours |
4. Select independently for each robot joint
A robot may use different architectures at different axes. Define each joint's load case rather than assigning all upper-body joints to harmonic gearing and all lower-body joints to planetary gearing. Check whether the selected configuration meets the required motion, package and control behavior.
For a humanoid leg, include stance, swing, contact and peak events. For an arm, include payload reach, acceleration and holding time. For a wrist, include tool moments, bearing loads and cable clearance. No percentage weight saving or battery gain follows from a mixed-architecture layout without a system comparison.
5. Compare installed cost and integration work
Include module price, mounting adapters, drive and power requirements, wiring, software, calibration, application validation and expected service work. Record document availability and supply assumptions. Obtain quotations for the same quantity and configuration before comparing total project cost.
If upgrading a CyberGear prototype, review CyberGear fit boundaries before selecting H or P. A larger torque number does not establish compatible mounting, voltage, command packets or thermal behavior.
Frequently asked questions
Is harmonic or planetary reduction better for a robot joint?
Select the exact configuration that meets torque-speed, lost-motion, stiffness, thermal, load and interface requirements. The gear family alone does not establish performance or suitability.
Does encoder compensation remove mechanical backlash?
Feedback control can improve positioning behavior, but does not physically remove clearance, compliance or wear. Specify and test mechanical lost motion separately from controlled positioning accuracy.
Does ZHR-P60 support native EtherCAT?
ZHR-P60 is CAN only and does not support native EtherCAT. Confirm interfaces for other ZHR-P models individually before design-in.
Request an H/P configuration comparison
Send continuous and peak torque, peak duration, speed, load cycle, available diameter and length, mounting loads, voltage, required protocol and quantity. Include your existing actuator model if this is an upgrade.
Review available technical documents
Submit your reducer and joint requirements