RoboTeam Twente Mars Rover Case Study: How CubeMars Meets the Motion Demands of Challenging Terrain

Building a Mars Rover for Challenging Terrain

A Mars rover is one of the representative applications in the field of mobile robotics. Unlike ordinary mobile robots that primarily operate on flat surfaces, Mars rovers must face complex environments such as uneven terrain, soft ground, loose rocks, and slopes. The robot must not only have sufficient driving force but also maintain controllability during movement, while taking into account the overall vehicle weight, structural space, and system integration requirements.

RoboTeam Twente is an interdisciplinary student robotics team from the Netherlands, with members from the University of Twente and Saxion University of Applied Sciences. The team focuses on robotics system development, involving multiple disciplines, including mechanical design, electronic systems, embedded control, software development, and artificial intelligence.

In the RoboTeam Twente Mars rover project, the team adopted a six-wheel drive configuration, with each wheel equipped with an independent motor. Among these components, the CubeMars AK70-10 KV100 is installed inside the wheel hub, serving as the wheel drive actuator and closely integrating the drive unit with the wheel structure.

For a project like this, the drive system is not simply a matter of selecting an individual component. The performance of the motor and actuator affects the power delivered to the wheels, the robot's response to motion commands, and the mechanical layout of the entire chassis.

Therefore, how to strike a balance between power output, motion response, and system integration is an important consideration in the design of a Mars rover drive system.

Challenges Facing the Drive System: Balancing Power and Control

During Mars rover development, the drive system needs to accommodate a variety of different motion conditions.

1. Complex Terrain Requires Sufficient Output Torque

When a robot travels on slopes, soft ground, or rocky surfaces, its wheels need to overcome ground resistance and load variations caused by the gradient. If the drive system cannot provide sufficient wheel-end torque, the robot may struggle to maintain its intended motion.

Therefore, when selecting a drive actuator, it is not enough to focus only on motor speed or size. It is also necessary to consider how the reduction mechanism converts motor output into the torque required at the wheels.

Wheel-end torque is an important indicator for evaluating driving capability, but it cannot independently determine a Mars rover's climbing or obstacle-crossing performance. Factors such as wheel radius, overall vehicle mass, ground traction, chassis structure, and load distribution also affect the robot's mobility on complex terrain.

2. Motion Response Affects Robot Maneuverability

A Mars rover does not always operate at the same speed. When adjusting travel speed, changing direction, or performing precise movement tasks, the drive system needs to respond promptly to control commands.

The gear reduction ratio is one of the key factors affecting actuator output speed and torque. A higher reduction ratio generally provides greater torque multiplication but reduces output speed, while a lower reduction ratio generally favors higher output speed.

This means that drive system design needs to be based on the robot's actual motion requirements rather than simply assuming that a higher reduction ratio is always better. The motor operating point, transmission efficiency, and control parameters also affect the actuator's actual output performance.

3. Limited Space Increases System Integration Complexity

A mobile robot chassis needs to reserve space for the wheels, suspension structure, battery, controller, and other mission equipment. If the motor, gearbox, encoder, and driver need to be installed and matched separately, mechanical layout and electrical integration may become more complicated.

For robotics development teams that need to work simultaneously on mechanical design, electronic systems, and software control, the level of actuator integration is also an important factor when evaluating a drive solution.

CubeMars Drive Solution: AK70-10 KV100 and Hub-Mounted Drive

For a six-wheel-drive mobile robot, actuator selection requires comprehensive consideration of output torque, speed, installation dimensions, and control interfaces. The CubeMars AK70-10 KV100 features a 10:1 planetary gearbox and integrates key components such as the motor, driver, and encoder, providing an option to evaluate for the mechanical layout and control integration of a robot drive system.

The reduction ratio determines the important trade-off between output speed and torque multiplication, while an integrated structure can help simplify the installation and matching of certain components. Both aspects deserve particular attention in space-constrained hub-mounted drive designs.

However, whether an actuator is suitable for a specific Mars rover platform still needs to be evaluated comprehensively based on the overall vehicle mass, wheel radius, target travel speed, terrain conditions, and heat dissipation requirements during continuous operation.

1. AK70-10 KV100: 10:1 Reduction Ratio and Hub-Mounted Drive

In the RoboTeam Twente project presentation, the CubeMars AK70-10 KV100 is shown as the wheel drive unit for the RoboTeam Twente Mars rover and is installed inside the wheel hub. This configuration combines the drive actuator with the wheel structure, providing a practical reference for chassis design and drive system integration.

According to the official CubeMars product specifications, the main parameters of the AK70-10 KV100 are as follows:

The AK70-10 KV100 uses a 10:1 planetary gearbox and integrates key components such as the motor, driver, and encoder into a single actuator. For mobile robotics development teams, this integration approach helps them plan the drive system around relatively well-defined dimensions, mounting interfaces, and control interfaces.

In a hub-mounted drive design, the actuator needs to provide sufficient output torque while also meeting requirements for target vehicle speed, installation space, and continuous operation. A lower reduction ratio generally favors higher output speed but provides relatively less torque multiplication. Therefore, a comprehensive evaluation is still required based on wheel dimensions, overall vehicle load, and actual terrain conditions.

In addition, an actuator's rated torque and peak torque are not equivalent to the vehicle's climbing or obstacle-crossing capability. Continuous output capability, allowable peak torque duration, transmission efficiency, heat dissipation conditions, and ground traction must all be included in the actual design and testing process.

Why Consider Integrated Actuators?

In addition to the output characteristics associated with different reduction ratios, actuator integration is another aspect of the RoboTeam Twente project worth discussing.

The CubeMars AK70-10 KV100 integrates key components, including the motor, gearbox, driver, and encoder, within a single housing. Compared with selecting and installing multiple components separately, an integrated solution offers the potential to simplify some mechanical installation and system-matching tasks.

For robotics development teams, this design approach offers several points of reference.

1. Simplifying Drive System Mechanical Layout

The actuator's external dimensions, mounting interfaces, and output structure directly affect chassis design. In the RoboTeam Twente project, the AK70-10 KV100 is installed inside the wheel hub, so the drive unit's dimensions and level of structural integration directly affect the wheel hub layout.

Using an integrated actuator allows developers to plan the structure around relatively well-defined dimensions and mounting interfaces, reducing some of the layout work required between separate components.

2. Enabling Coordinated Development of Mechanical and Control Systems

Robot drive solutions need to address mechanical installation, power supply configuration, communication interfaces, control methods, and feedback signals simultaneously. Clarifying the actuator's interfaces and control capabilities in advance helps the mechanical, electronics, and software teams coordinate their integration work around the same drive solution.

This does not mean that an integrated actuator eliminates the need for system commissioning. Power supply, current limits, communication protocols, control parameters, and thermal design still need to be verified according to the product documentation and the overall vehicle requirements.

3. Providing Configuration Flexibility for Different Motion Requirements

RoboTeam Twente adopted a six-wheel drive configuration, with each wheel equipped with an independent motor. This design requires consideration not only of the output capability of each actuator but also of the communication configuration, parameter calibration, and coordinated control of multiple drive units.

In the project video presentation, the team demonstrates the process of assigning independent IDs to the motors, connecting them to the control system through a shared communication bus, and progressing from calibrating a single motor to starting all six wheels in coordination.

These details show that the application of integrated actuators involves not only mechanical installation but also coordination with communication configuration, control interfaces, and full-vehicle integration and commissioning.

What Can We Learn from the RoboTeam Twente Case Study?

The RoboTeam Twente project demonstrates the application of compact integrated actuators in a six-wheel mobile platform and provides several useful selection considerations for other mobile robotics projects.

1. Evaluate Installation Space in Conjunction with the Wheel and Chassis Structure

In addition to the actuator's outer diameter, it is necessary to consider axial length, mounting interfaces, cable routing, and maintenance space. For multi-wheel platforms, the dimensions and weight of each drive unit also affect the overall vehicle layout.

Therefore, actuator selection should be based on an overall design that considers the wheel hub, suspension structure, and chassis space, rather than judging suitability solely by the actuator's outer diameter.

2. Calculate Wheel-End Output Requirements Based on Actual Operating Conditions

Vehicle weight, wheel radius, slope, ground resistance, and obstacle-crossing requirements all affect the required torque. Short-term peak loads and continuous operating requirements should be evaluated separately, with an appropriate margin for actual operating conditions.

Rated torque and peak torque must be evaluated separately, while continuous output capability, transmission efficiency, and heat dissipation conditions must also be considered. Product specifications are only the starting point for actuator selection and cannot directly replace full-vehicle performance validation.

3. Balance the Reduction Ratio with the Target Vehicle Speed

A higher reduction ratio helps provide high torque at low speeds but also limits output speed. During selection, calculations and verification should account for target vehicle speed, wheel-end torque, and dynamic response.

For mobile robots, the appropriate reduction ratio is neither simply the highest nor the lowest possible. Instead, it should provide a suitable balance between driving force, maximum speed, and motion response for the specific task.

4. Plan the Control System in Advance

For platforms with six or more drive units, it is necessary to confirm communication interfaces, control modes, feedback data, and power supply configuration, while also planning motor IDs, bus connections, and commissioning procedures.

When multiple drive units operate in coordination, communication load, control command management, and fault-handling mechanisms also require attention. For robots designed for long operating periods, temperature rise, heat dissipation, and continuous output performance should also be verified.

The final selection of a drive actuator must ultimately be based on the overall vehicle requirements. Only through prototype testing of torque, speed, temperature rise, communication stability, and actual terrain performance can developers determine whether a drive solution is suitable for the target application.

Conclusion

The RoboTeam Twente Mars rover project demonstrates the importance of the drive system in the development of mobile robots designed for complex terrain. From the compact drive layout inside the wheel hubs to the independent drive and coordinated control of all six wheels, every drive system design decision needs to be evaluated in conjunction with the robot's actual mission requirements.

In this case, the CubeMars AK70-10 KV100 serves as the Mars rover's hub-mounted drive actuator. It features a 10:1 planetary gearbox and integrates key components, including the motor, driver, and 14-bit encoder, within a single housing. Its rated torque is 8.3 N·m, and its peak torque is approximately 24.8 N·m, providing specific product parameters for evaluating compact hub-mounted drive solutions.

For Mars rover and other mobile robotics projects, selecting an appropriate drive solution involves more than choosing a motor with impressive specifications. The actuator's output characteristics must match the overall vehicle load, wheel parameters, motion objectives, and control system. At the same time, installation space, power supply conditions, thermal management, communication capabilities, and continuous operating performance should also be incorporated into the overall design and validation process.

Through the RoboTeam Twente project, robotics developers can gain a deeper understanding of how to evaluate actuator output performance and integration methods based on practical application requirements, while considering power performance, mechanical layout, and multi-motor control requirements together. The CubeMars AK Series integrated actuators provide drive solutions for evaluation in robot design, while the specific model should be selected according to project operating conditions and official technical specifications.

If you are developing a Mars rover, an off-road mobile robot, or another robotic platform requiring a compact drive system, you can explore the CubeMars AK Series actuators further and identify a drive solution suitable for your project based on your load, speed, and control requirements.