Hub Motor vs Drive-Steering Unit vs Differential Module for AGVs
Key takeaways
- There are four common ways to drive an AGV or AMR wheel: a hub motor (motor inside the wheel), an integrated servo wheel (driver, motor, gearbox and wheel in one housing), a drive-steering unit (the wheel is actively steered) and a differential drive module (two independently driven wheels in one module).
- The choice is driven by load per wheel, required travel speed, chassis height, turning behaviour and how much integration work you want to do, in roughly that order.
- Rule of thumb from JY Robot's product ranges: hub motors and integrated servo wheels up to about 2 t vehicles; differential drive modules from 1 to 8 t; drive-steering units from 600 kg to 6 t per unit and, in multi-unit layouts, well beyond.
- Omnidirectional motion needs either several steered units or Mecanum/omni wheels; it is not a property of the motor type.
The four architectures at a glance
| Hub motor wheel | Integrated servo wheel | Drive-steering unit | Differential drive module | |
|---|---|---|---|---|
| What it is | Motor built into the wheel hub, usually gearless or with an internal planetary stage | Servo driver, motor, planetary gearbox and wheel in one unit; one connector | Drive motor plus a steering motor; the wheel turns about a vertical axis | Two driven wheels, two motors and gearboxes on one mounting frame |
| Steering | Differential, by pairing two wheels | Differential, by pairing two wheels | Active, per unit | Differential, built in |
| Typical load per unit (JY Robot ranges) | Light vehicles; e.g. 5.5-inch hub motor with 8.5 N·m rated / 25.5 N·m peak torque | Vehicles of 0.6–2 t with Ø165/Ø180 mm wheels, 22–75 N·m rated torque | 600–3,000 kg single-support, 800–6,000 kg double-support, 800–3,000 kg vertical | 1,000–8,000 kg per module |
| Typical speed | Up to about 1.5 m/s | About 1.2–2.1 m/s | Up to 147 m/min (about 2.4 m/s) on vertical units | Up to about 56 m/min |
| Chassis height | Lowest | Low | Horizontal units low; vertical units taller but smaller footprint | Low to medium |
| Zero-radius turn | Yes (two wheels) | Yes (two wheels) | Yes with two or more units; a single unit needs a turning radius | Yes |
| Tyre scrub in curves | Higher | Higher | Lowest | Higher |
| Integration effort | Low mechanically, but you supply the driver | Lowest: cable in, motion out | Medium: two axes to control | Low: one frame, two motor drives |
| Best for | Light service and warehouse robots, tight height budgets | Compact AMRs up to 2 t, fast development | Precise tracking, heavy loads, forklift-type AGVs, omnidirectional platforms | Underride AMRs, pallet movers, heavy platforms needing pivot turns |
Hub motor wheels
A hub motor puts the motor inside the wheel, so the drivetrain disappears into the wheel envelope. That gives the lowest possible chassis height and a very simple mechanical interface: an axle, a bracket and a cable. The trade-off is torque. Without a large external gearbox, a hub motor delivers modest torque at the wheel, so it suits lighter vehicles and flat floors. JY Robot's 5.5-inch integrated servo hub motor combines the servo drive with the hub motor, Ø140 mm polyurethane tyre, 8.5 N·m rated and 25.5 N·m peak torque at 1.54 m/s rated speed; the 7030/8030 hub drive wheels are 24 V units for light differential platforms.
Choose a hub motor when height and simplicity matter more than gradeability and payload, and when the floor is smooth.
Integrated servo wheels
An integrated servo wheel keeps the gearbox, so it delivers far more torque than a hub motor at similar size, while still packing the driver, motor, reducer and wheel into one housing with a single connector. For an AMR builder this is the fastest route from drawing to driving: there is no driver cabinet to wire and no motor-gearbox-wheel alignment to design. JY Robot's common-body ISW modules and the dual-STO version for 0.6–2 t vehicles cover Ø165/Ø180 mm wheels, 22–75 N·m rated torque and 1.18–2.14 m/s. A vertical integrated steering wheel adds active steering in the same integrated format for lighter vehicles.
Choose an integrated servo wheel for compact AMRs up to about 2 t, when development time and a clean electrical architecture are priorities. If your safety concept requires STO at the drive, pick the STO variant and read our STO supplier checklist.
Drive-steering units
A drive-steering unit (steering drive wheel, "Lenkantrieb" in German) drives the wheel and also turns it about a vertical axis with a second motor and an angle encoder. Because the wheel is steered rather than skidded, the vehicle follows curves without tyre scrub, tracks precisely under heavy load and can combine several units into omnidirectional platforms. The cost is a second axis to control and a taller or wider unit. JY Robot offers horizontal single-support units for 600–3,000 kg, horizontal double-support units for 800–6,000 kg and vertical units for 800–3,000 kg at up to 147 m/min.
Choose drive-steering units for heavy loads, long travel at speed, forklift-type and tugger AGVs, and any platform where tracking accuracy and tyre life matter. Our steering drive selection guide lists the nine inputs that decide the size, and horizontal vs vertical explains the two layouts.
Differential drive modules
A differential drive module packages two driven wheels, two motors and two gearboxes on one frame. The vehicle controller commands two wheel speeds and the module does the rest: straight travel, curves and pivot turns on the spot. Compared with two separate servo wheels, the module gives you one mechanical interface, matched wheels and a load-bearing frame that can carry a lifting mechanism on top, which is why it dominates underride and pallet-moving AMRs. JY Robot's differential drive modules cover 1–8 t at 48 V, and a hydraulic lifting version covers 6–20 t.
Choose a differential module for underride and pallet-handling vehicles, heavy platforms that must pivot in place, and whenever you want the drive and the lifting mechanism on one frame. The detailed comparison with steered units is in Differential Drive vs Drive-Steering Units.
A decision table
| Your requirement | Usual answer |
|---|---|
| Vehicle under about 500 kg, smooth floor, lowest height | Hub motor wheels (pair) |
| Compact AMR up to 2 t, fastest integration, single connector per wheel | Integrated servo wheels (pair) |
| Underride or pallet AMR, 1–8 t, pivot turns, lift on top | Differential drive module |
| Heavy platform, long runs, precise tracking, low tyre wear | Drive-steering units (two or four) |
| Forklift or tugger AGV | One or two drive-steering units with castors |
| Omnidirectional heavy-duty platform | Four drive-steering units, or Mecanum modules for lighter loads |
| Ramps above about 3–5 %, or outdoor | Drive-steering units or differential modules with larger wheels and higher torque; check the sustained torque, not only the cycle average |
Three checks before you commit
- Load per driven wheel, including load transfer on ramps and during braking, not the gross vehicle weight. Our tractive force and wheel load guide shows the method.
- Sustained torque for the worst segment, such as a ramp or a long haul, compared with the motor's continuous rating. See motor sizing with a worked example.
- Interfaces and safety: CANopen or EtherCAT, encoder and brake control, and whether STO is required. See CANopen vs EtherCAT vs RS-485.
FAQ
Is a hub motor the same as an integrated servo wheel?
No. A hub motor has the motor inside the wheel and usually little or no gearing, so it is the flattest option but torque-limited. An integrated servo wheel keeps a planetary gearbox and adds the driver, so it delivers much more torque in one housing.
Can I build an omnidirectional AGV with differential drive modules?
A differential module can pivot on the spot but cannot move sideways. True omnidirectional motion needs four steered drive units or Mecanum/omni wheels.
Which option has the lowest total cost?
For light vehicles, hub motors or integrated servo wheels are cheapest overall because they remove drivers, gearboxes and alignment work. For heavy vehicles, a differential module is usually cheaper than two drive-steering units of the same capacity, but steering units save tyre and floor wear over the life of the vehicle.
What does JY Robot need to recommend a drive?
Total and peak load, target speed, acceleration, maximum gradient, wheel count and layout, available height, floor type, duty cycle and the control interface. Send these to info@jy-robots.com and you get a series and a starting configuration.