Integrated Servo Wheel for AGV/AMR: Selection Guide
An integrated servo wheel combines several drive functions into one compact wheel module. Depending on the architecture, the assembly may integrate the servo drive, motor, gearbox, encoder and polyurethane wheel, or use a compact servo hub-motor structure.
For AGV and AMR projects, the correct model should not be selected from vehicle payload alone. Wheel-end torque, actual wheel load, target speed, chassis geometry, voltage, communication interface, safety requirements and installation space all affect the final choice.
1. What Is an Integrated Servo Wheel?
A conventional mobile-robot drivetrain may use a separate servo drive, motor, gearbox, coupling and drive wheel. This gives the designer flexibility, but also requires more installation space, wiring and mechanical interfaces.
An integrated servo wheel combines several of these functions into one assembly. For compact AGV and AMR chassis, this can reduce wiring, shorten assembly time and simplify replacement.
The first question is therefore not simply “How many kilograms can the robot carry?” Selection should start from the forces acting at the wheel.
2. Three Integrated Servo Wheel Architectures
2.1 Common-Body Integrated Servo Wheel
The common-body architecture integrates the servo drive, motor, reduction gearbox and wheel in one module while using external plug-in cable assemblies.
JY Robot's common-body integrated servo wheel series uses Ø165 mm and Ø180 mm polyurethane wheels, with rated wheel torque from 22 to 75 N·m and rated linear speed of approximately 1.18 to 2.14 m/s.
This architecture is suitable when compact packaging, standardized chassis construction and convenient field replacement are priorities.
2.2 STO Integrated Servo Wheel
The STO integrated servo wheel series uses a similar mechanical drive concept but adds dual Safe Torque Off inputs and dual isolated encoder-signal outputs, together with CANopen and Modbus RTU communication.
STO can prevent the drive from generating motor torque when correctly integrated into the vehicle safety system. It does not replace the complete vehicle safety design, brake analysis or safety validation.
2.3 Integrated Servo Hub Motor
A servo hub motor uses a more compact wheel-centered structure. The JY-IHM140-085-48-C integrated servo hub motor uses a Ø140 mm polyurethane wheel, 8.5 N·m rated torque, 25.5 N·m maximum torque and 1.54 m/s rated speed.
Its permissible radial load is 1500 N and the complete unit is rated IP65. This architecture is suitable for compact mobile robots where installation volume and protection level matter more than the higher torque and wheel load available from larger geared servo wheels.
3. Start with Required Tractive Force, Not Motor Power
Motor power alone does not show how much driving force reaches the floor. Wheel-end torque and wheel radius give a more useful starting point.
F = T / r
F is theoretical wheel tractive force in newtons, T is wheel-end torque in N·m, and r is effective loaded wheel radius in metres.
For example, a Ø180 mm wheel with 40 N·m rated torque has a nominal radius of 0.09 m:
F = 40 / 0.09 ≈ 444 N
This is a theoretical wheel-end value. Actual usable traction may be lower because floor friction, polyurethane deformation, acceleration demand, gradients and vehicle load distribution all affect the force that can be transmitted without slip.
See our AGV/AMR tractive force and wheel-load calculation guide for the complete calculation method.
4. Wheel Load and Vehicle Payload Are Not the Same
A specification such as “maximum radial load 7000 N” refers to allowable mechanical load acting on that wheel module. It should not simply be multiplied by the number of wheels and treated as AGV payload capacity.
The load on each drive wheel depends on the vehicle centre of gravity, wheelbase, caster arrangement, suspension or floating mechanism, payload position and acceleration condition.
A four-wheel platform with a centred payload does not necessarily maintain a perfect 25/25/25/25 percent wheel-load distribution on a real floor. Frame stiffness and floor unevenness can transfer substantially more load to one wheel.
Calculate the expected reaction force at each driven wheel first, then compare the worst-case value with the permissible radial load of the selected module.
5. Match Wheel Torque and Speed Together
Higher reduction normally increases available wheel torque but reduces wheel speed. Selecting only the highest-torque model may therefore create an unnecessarily slow vehicle.
Linear wheel speed can be estimated from:
v = π × D × n / 60
where D is wheel diameter in metres and n is wheel speed in rpm.
For the Ø180 mm integrated servo-wheel family, different reduction ratios provide different combinations of wheel torque and travel speed. The correct model depends on acceleration, continuous travel speed and required traction.
6. Rated Torque and Peak Torque
Peak torque is useful for acceleration and short disturbances, but it should not be treated as the normal continuous design point.
The wheel should normally handle expected travel resistance, gradients and acceleration within its appropriate rated operating region. Peak capability should remain available for short transient conditions.
7. Voltage, Logic Power and Communication
Electrical compatibility should be checked before the mechanical design is frozen.
The current JY Robot integrated servo-wheel families use low-voltage DC drive architecture with separate drive-power and logic-power supplies. CANopen is available for vehicle-controller communication, while the STO series also supports Modbus RTU.
A broad drive-voltage range does not mean the actual vehicle battery voltage can be ignored. Available speed, current demand, regenerative energy and braking-resistor requirements should still be checked.
The controller engineer should confirm battery voltage, logic supply, CANopen requirements, node-ID arrangement, digital I/O, encoder feedback and braking strategy.
8. When Is STO Worth Selecting?
STO is not simply an additional communication function. It is a safety-related method of preventing the drive from generating motor torque when activated through the intended safety circuit.
If the AGV or AMR uses a safety PLC, safety laser scanner, safety relay or similar architecture, an STO-capable wheel can simplify the interface between the traction system and the overall safety design.
STO does not mechanically hold the vehicle in position. Vehicle mass, stopping distance, brake configuration, slope operation and risk assessment remain system-level engineering tasks.
9. Installation Space Is More Than Wheel Diameter
The wheel diameter is only one part of the installation envelope. The chassis designer should also check module width, mounting-hole pattern, connector direction, cable bend radius, maintenance access and ground clearance.
The common-body architecture can be useful when modules need to be exchanged quickly because the external cable connections are detachable.
For a very compact robot, the Ø140 mm servo hub motor may offer a better packaging solution even though its torque and permissible radial load are lower than those of the larger Ø165/180 mm geared servo-wheel family.
10. Check Duty Cycle and Thermal Conditions
An AGV travelling continuously for long distances places a different thermal load on the drivetrain from a robot that moves for several seconds and then remains stationary during loading or processing.
Duty ratings therefore need to be considered together with torque and current. The JY-IHM140-085-48-C hub motor, for example, is specified for S3 intermittent periodic duty with a 10-minute cycle and 60% operating time.
Applications with long ramps, frequent acceleration, high ambient temperature or extended continuous travel should be reviewed separately.
11. Practical Selection Example
Assume an AMR requires approximately 1.5–2.0 m/s travel speed and uses two driven wheels. The chassis team is considering an Ø180 mm integrated servo wheel.
A 40 N·m rated wheel provides approximately 444 N theoretical wheel-end force. Two driven wheels therefore provide about 888 N theoretical combined force if both wheels can transmit the force to the floor.
The engineer should then compare this with rolling resistance, acceleration force and gradient force, and verify that enough normal force exists on the driven wheels to avoid slip.
The actual radial load on each module must also be checked, followed by vehicle speed, peak torque, duty cycle, battery voltage, CANopen integration and installation space.
12. Information Required for Selection
- AGV/AMR self-weight and maximum payload;
- number and position of drive wheels and casters;
- centre of gravity or estimated drive-wheel load;
- target and maximum travel speed;
- required acceleration and deceleration;
- floor type and maximum gradient;
- battery and DC-bus voltage;
- CANopen, Modbus, I/O and safety requirements;
- available mounting envelope;
- expected operating duty cycle.
13. Which Architecture Should You Evaluate First?
| Application Priority | Architecture |
|---|---|
| Standardized chassis, quick replacement and higher wheel torque | Common-body integrated servo wheel |
| Safety-controller integration or STO requirement | STO integrated servo wheel |
| Compact robot, smaller envelope and IP65 requirement | Integrated servo hub motor |
This table is only a starting point. Final selection should still be checked against wheel torque, actual radial load, speed, duty cycle, electrical architecture and installation dimensions.
14. Engineering Selection Support
JY Robot supplies integrated drive components for AGV, AMR and mobile-robot platforms. For model selection, provide vehicle weight, payload, wheel arrangement, target speed, gradient, installation space, supply voltage and control requirements.
For substantially higher wheel loads or a different chassis architecture, an integrated servo wheel may not be the best solution. A differential drive module may provide a more suitable mechanical layout.