Last March, students from Kyungnam University majoring in robotics visited Bon Systems.
As artificial intelligence (AI) and robotics continue to emerge as central themes in the Fourth Industrial Revolution, the students were eager to move beyond theory and gain hands-on experience with real hardware. Their enthusiasm filled the space from the very beginning.
To support students who had limited opportunities to work directly on robotic hardware during their AI studies, Bon Systems hosted a “Make a Robot Dog” workshop. This hands-on session allowed them to experience the core processes of robot development in a practical and immersive setting.
Understanding the Actuator
After a brief welcome, we introduced Bon Systems’ core technologies and business areas, followed by an explanation of the project’s objectives and how the workshop would proceed. Once the students understood the sequence of tasks and their significance, they began the assembly process right away.
The first step of the Make a Robot Dog project was assembling the actuator. In this phase, students worked on integrating the actuator—an essential component that enables the robot’s legs to move—into the mechanical structure. The focus was placed on helping them understand the overall motion mechanism through hands-on assembly.
An actuator is a drive unit that combines a motor and a reducer (gearbox) into a single integrated system.
In this configuration, the reducer plays a key role by lowering the motor’s rotational speed while simultaneously increasing torque output—allowing the system to generate greater force.
This concept is similar to how a bicycle shifts to a lower gear when climbing a hill, making it easier to pedal with less effort.
For this assembly, we used the BCSA110-029-H-FOR-V1 model actuator. It features a diameter of 110 mm, a reduction ratio of 29:1, and is capable of delivering a rated output torque of up to 37 Nm.
Before beginning the full assembly, we briefly introduced the components that make up the actuator used in this project.
Bon Systems’ cycloidal actuator consists of the following key parts: bearings, a cycloid disk, an eccentric shaft, output pins, pin rollers, a frameless motor, and a housing.
In the future, this actuator is expected to be released as a smart actuator type that integrates control devices such as drivers, inverters, and brakes. Research and development toward that goal is actively ongoing.
A frameless motor, as the name implies, is designed without an external housing. It exposes both the stator (coil) and the rotor (magnet), allowing for greater flexibility in mechanical integration and more efficient use of space.
The BCSA 110 model used in this project incorporates a cycloidal reducer directly within the frameless motor, resulting in a compact and highly integrated actuator design.
Assembly Begins
Actuator assembly starts with the combination of the output shaft and the bearing.
The bearing is first mounted onto the output shaft, which is then inserted into the housing, followed by the installation of the output pin.
Next, the bearing is assembled onto the eccentric shaft, followed by the installation of the cycloid disk.
The next step is to assemble the eccentric shaft onto the output shaft. At this stage, it is essential to align the position of the output pin and the orientation of the output shaft precisely before insertion.
Careful inspection of the alignment between all components is crucial, as any assembly error can have a direct impact on the overall driving performance.
After inserting the roller pins, the internal gear is assembled.
Before that, grease is applied to the contact surfaces. This step is essential to prevent wear or damage caused by friction between the internal gear and the cycloid disk.
If components like bearings do not fit properly during the assembly process, dedicated jigs and press-fit machines are used.
Once the frameless outer motor—one of the key features of the BCSA 110 model—is installed and the housing is assembled, the first step in building a quadruped robot, the actuator assembly, is complete.
Finally, Make a Robot Dog
We have now entered the full-scale assembly phase of the quadruped robot.
Since the robot’s main frame requires four legs in total, the students were divided into teams, with each team responsible for assembling one leg.
The main components used in this phase are as follows.
Although not visible in the photo, each leg of the quadruped robot requires a total of three actuators for assembly.
The scene shown here captures the process of assembling the bracket. In this step, two actuators are installed on different axis directions. This configuration is essential to allow the robot to move in multiple directions.
If only one actuator is installed, movement is limited to a single axis—either forward and backward or side to side.
However, by mounting two actuators on different axes, such as vertical and horizontal, one can produce linear motion (left-right or up-down), while the other enables rotational movement.
This kind of configuration allows the robot to perform more complex movements and plays a critical role in achieving higher levels of motion autonomy.
For example, if we consider the leg of a quadruped robot, a joint that moves only in the forward and backward direction allows for linear movement, but such single-axis motion alone is not sufficient to achieve stable and natural walking behavior.
To overcome this limitation, each leg is equipped with three actuators, enabling not only forward and backward motion but also directional changes and balance control.
By adopting this type of multi-degree-of-freedom structure, the robot gains greater flexibility and stability in its movements, allowing it to adapt effectively to various ground conditions.
Watching the students stay focused and engaged throughout the assembly process, we also found a sense of fulfillment in guiding and supporting them along the way.
After completing the actuator assembly, the next step is attaching the legs.
Since the screw holes had to be aligned precisely during assembly, working with the frame in a horizontal position was somewhat inconvenient and presented a few challenges.
This scene shows the process of installing the timing belt and inserting the idler. The idler is a component that helps maintain consistent tension by adjusting the tightness of the timing belt.
The assembly of all the lower legs has been completed.
The leg actuation mechanism of a quadruped robot can be implemented in various ways, not only with timing belts but also through chain drives or linkage systems.
Each method has its own strengths and limitations, so rather than declaring one as superior, it is important to consider the robot’s intended use, operational goals, and working environment to determine the most efficient approach.
As the fully assembled legs are mounted onto the main body, the project enters its final stage.
The robot’s body was constructed using 20T aluminum profiles, providing a lightweight yet stable structure.
The quadruped robot development project with the students of Kyungnam University, which took place over several hours, was successfully completed.
This hands-on workshop focused primarily on hardware assembly. The completed robot will be handed over to the students so that they can continue developing the software and explore its actual operation.
We hope that this experience will serve as a valuable learning opportunity and help students build practical, real-world engineering skills.
Appendix
In this appendix, we briefly introduce some of the key components and terms that were not covered in detail during the Make a Robot Dog project.
Why is an idler necessary in a timing belt system?
An idler plays a critical role in adjusting the tension of the timing belt and maintaining the stability of its path.
If the belt tension is not consistent, it can become loose or slip during rotation, leading to instability in power transmission.
The idler helps prevent such issues by ensuring that the belt moves along a fixed path with proper tension, making it an essential supporting component in belt-driven systems.
What are the key components of a robot dog?
The core components of a quadruped robot begin with its body and legs. The body serves as the central structure that connects all other parts and houses the control systems and power supply.
Each leg typically consists of multiple joints, driven by actuators, and is designed based on a multi-degree-of-freedom architecture to enable complex movements.
To accurately perceive its surroundings and monitor its own state, the robot is equipped with various sensors.
For example, a LiDAR sensor allows the robot to scan its environment in 360 degrees, enabling autonomous path planning and obstacle avoidance.
A gyroscopic sensor continuously measures the robot’s tilt to help maintain a stable center of gravity during movement.
For the entire system to operate reliably, sufficient and efficient power supply is essential.
Since the battery directly affects the robot’s center of mass, both its capacity and placement must be carefully considered to ensure stable operation.
Why was BCSA used in the Make a Robot Dog project?
In a quadruped robot, each leg joint must move independently while maintaining balance, making it essential to use a compact yet powerful actuator.
The BCSA (Bon Cycloid Smart Actuator) series used in this workshop was selected because it meets these exact requirements in both structure and performance.
Despite its compact size, BCSA provides a high reduction ratio, which enables stable high-torque output and excellent durability.
Its flat-profile design, based on a frameless motor architecture, offers a high degree of design flexibility, making it easy to integrate into various robot configurations.
Where can I see the full assembly process?
Bon Systems carries out various robot development projects based on its proprietary cycloidal reducer technology.
The Make a Robot Dog project introduced here is one example where this technology was applied in a real-world setting.
If you’re interested in the full assembly process or would like to see the workshop atmosphere firsthand, you can watch the complete video on Bon Systems’ official YouTube channel. Please refer to the link below to view the video.
