Low-Profile AGV/AMR Drive System for Underride Robots
Underride AGVs and low-profile AMRs are usually constrained by packaging before motor power becomes the main problem. The drive wheel, steering mechanism, lifting module, chassis structure and ground clearance all compete for the same vertical space.
For this type of robot, drive selection should start with the available installation envelope, wheel diameter, driven-wheel load and required motion. A module that meets the load rating can still be unsuitable if the wheel or steering structure forces the chassis too high.
1. Start With the Chassis Envelope
Before choosing a drive unit, define the maximum space available below the payload or rack interface. The key dimensions are not only overall height, but also wheel diameter, ground clearance, mounting interface, motor envelope and the space needed for steering or lifting movement.
JY Robot horizontal drive-steering units use wheel sizes from Ø150 × 55 mm to Ø280 × 80 mm, while the differential-drive range uses wheels from Ø160 × 70 mm to Ø300 × 130 mm. The smallest wheel is not automatically the best choice: wheel load, floor joints and required traction still have to be checked.
2. Horizontal Drive-Steering or Differential Drive?
A horizontal drive-steering unit separates traction and wheel-angle control. This can be useful when the chassis needs independently controlled wheel direction, precise docking or coordinated multi-wheel steering.
The current horizontal series covers 600–3,000 kg load capacity with rated tractive force from 508 to 2,910 N, depending on configuration.
A twin-wheel differential drive module uses the speed difference between two driven wheels to turn. It can suit compact underride platforms that need forward/reverse travel and pivot turning without a separate steering actuator.
The current differential-drive series covers 1,000–8,000 kg load capacity with several wheel, motor and tractive-force configurations. Selection should still be based on driven-wheel load and required traction rather than vehicle mass alone.
3. Lifting Stroke Uses the Same Packaging Space
Many underride robots also need to lift a rack, shelf or payload after entering beneath it. That means the lifting mechanism must be evaluated together with the drive system, not after the chassis has already been fixed.
JY Robot ball-screw lifting modules cover 200–2,000 kg load capacity with 50–100 mm configurable lifting stroke. Standard lifting speed is 8.3 mm/s, and the rotary section can operate at 90°/s.
The required retracted installation height is project-dependent, so the chassis drawing and available mounting space should be checked before selecting the lifting configuration.
4. Smaller Wheels Reduce Height, but They Change the Rest of the Design
A smaller drive wheel can help reduce chassis height, but wheel diameter should not be reduced in isolation. Smaller wheels generally increase sensitivity to floor joints, gaps and local surface irregularities, and they can change the required motor speed and reduction ratio for the same vehicle speed.
For an underride robot, wheel selection therefore has to balance chassis height against floor-crossing capability, tyre load, required travel speed and available traction. The lowest possible wheel diameter is not always the best engineering choice.
5. Driven-Wheel Load Still Determines Usable Traction
A low-profile chassis often distributes much of the vehicle mass through separate support or load wheels. That can leave the drive wheel with less normal load than expected from the gross vehicle weight.
Usable traction is limited by the friction available at the driven wheel:
Fmax = μ × Ndrive
This means a drive module can have sufficient motor torque but still slip if the driven-wheel load is too low. Centre-of-gravity position, payload transfer and support-wheel layout should therefore be checked before selecting the drive configuration.
6. Drive and Lifting Systems Must Be Packaged Together
In an underride AGV, the drive module and lifting module usually compete for the same central chassis volume. Designing them independently can create conflicts in mounting height, service access, structural load paths and cable routing.
A practical layout review should therefore include the drive wheel envelope, steering sweep where applicable, lifting-module retracted height, required lifting stroke, chassis structure, battery space and ground clearance in the same drawing.
For applications using the 50–100 mm lifting-stroke range, the required stroke should be confirmed from the rack or load interface rather than choosing the maximum stroke by default.
7. A Practical Underride AGV Selection Workflow
| Step | Engineering Check | Why It Matters |
|---|---|---|
| 1 | Define maximum chassis and entry height | Sets the packaging limit for drive, wheels and lifting components |
| 2 | Confirm wheel load distribution | Determines load capacity and available traction at the driven wheels |
| 3 | Choose required vehicle motion | Defines whether differential drive or independent steering is more appropriate |
| 4 | Check wheel diameter and floor condition | Balances low profile against joints, gaps, traction and travel speed |
| 5 | Define lifting load and stroke | Prevents drive and lifting systems from competing for the same space later |
| 6 | Review the complete chassis drawing | Confirms mounting, ground clearance, service access and interface compatibility |
For independent wheel-angle control, review the horizontal AGV drive-steering unit. For compact pivot-turning layouts, see the dual-wheel differential drive module. For integrated load lifting and rotation, see the ball-screw lifting module.
8. Which Drive Architecture Fits a Low-Profile Robot?
| Chassis Requirement | Horizontal Drive-Steering | Differential Drive |
|---|---|---|
| Independent wheel-angle control | Strong fit | Not the normal function |
| Compact pivot turning | Possible with suitable chassis layout | Natural operating mode |
| Multi-module coordinated steering | Well suited | Usually not the first choice |
| Simple twin-wheel traction layout | More steering hardware required | Strong fit |
| Very restricted vertical packaging | Horizontal layout can help | Must be checked against wheel and module envelope |
| Heavy driven-wheel load | Configuration-dependent | Available in higher-load configurations |
The correct architecture should be selected from the required vehicle motion and packaging constraints together. A low chassis height alone is not enough reason to choose either system.
9. Common Low-Profile AGV Design Mistakes
- Selecting the smallest wheel first: this may reduce chassis height but can create problems with floor joints, wheel load and required wheel speed.
- Using gross vehicle weight as the drive-wheel load: support wheels may carry a large share of the total mass, reducing usable traction at the driven wheels.
- Choosing the drive before defining the lifting system: the drive, lift, battery and chassis structure may later compete for the same installation volume.
- Ignoring steering sweep: a module may fit statically but interfere with the chassis, cables or lifting structure while steering.
- Checking only straight-line traction: frequent pivot turning can introduce additional tyre scrub and turning resistance.
- Freezing the chassis too early: wheel diameter, mounting interface and lifting stroke should be reviewed before the structural layout is finalized.
For an underride AGV or low-profile AMR project, the most useful starting information is a chassis drawing showing the available installation envelope, vehicle mass, expected wheel-load distribution, required motion, floor condition, lifting load and lifting stroke.