A robot joint is a part where shock and load changes occur frequently, as in walking, climbing stairs, and grasping and moving objects. The ankle, knee, and hip must support the robot’s weight while receiving the force transmitted from the ground, and the arm and wrist can encounter situations of colliding with an object during work or receiving a larger-than-expected force. On top of this, because the space inside a joint is very limited, accurate operation, stable power transmission, and reliability over long-term operation must be considered together.
This article looks at the operating environment in which humanoid joints are placed and explains what role a Cycloidal gearbox can play in a joint structure where shock and repeated loads occur. It also organizes why the advantage of realizing a wide range of reduction ratios in a single-stage structure, along with a slim structure, a Pinless design, and a design direction that reduces the part count, is treated as important in humanoid joints.
Table of Contents
The Operating Environment of Humanoid Joints
Key Summary — The joint is continuously exposed to the force transmitted from the ground during walking, the shock that occurs when going up and down stairs, and the load changes that arise when grasping and moving objects. A structure that can stably transmit force during repeated operation, not just accurate operation, matters.
A humanoid robot joint moves under different conditions than the drive unit of general automation equipment. Unlike equipment that repeats a set motion in a fixed position, a humanoid must perform complex motions such as walking, changing direction, maintaining balance, and handling objects. In this process, not only is a constant force transmitted to each joint, but momentary shock, repeated loads, and force changes due to contact can occur together.
The lower-body joints in particular must receive both the robot’s weight and the force rising from the ground during walking. Because the ankle, knee, and hip must generate movement while maintaining the robot’s posture, they are continuously exposed to repeated load changes. When going up and down stairs or moving over uneven floors, the burden transmitted to the joints can grow larger.
The same is true for the upper-body joints. The shoulder, elbow, and wrist can receive a larger-than-expected force in the process of lifting, pushing, or pulling an object. Situations of colliding with the work target or of the object’s center of gravity changing must also be considered. The Cycloidal gearbox that goes into a humanoid joint must therefore be able to maintain stable operation amid repeated load changes, beyond simply generating movement.
For humanoid joints, withstanding momentary shock matters, but the joint’s movement must also remain stable even after moving repeatedly for a long time. For this reason, the reducer structure, the part count, the way loads are borne, and the use of the space inside the joint become important review elements in humanoid design.
The Durable Cycloidal Reducer
Key Summary — A humanoid robot receives shock at its lower-body joints with every step. The Cycloidal gearbox can draw attention as a structure that stably transmits force in these environments through its surface-contact-based load-distribution structure.
A humanoid robot receives shock at its lower-body joints with every step it takes. At the moment the foot meets the floor, force rises from the ground, and in the process of maintaining body balance, load changes occur at the knee and hip. When using the arms to grasp or move an object, force changes continuously occur at the joints as well. In this way, a humanoid joint is close to an environment where shock and load changes are repeated, not one that needs only smooth rotation.
The Cycloidal gearbox can draw attention as a structure that stably transmits force in these environments. Its surface-contact-based load-distribution structure can help reduce the burden of shock concentrating on a specific area, and it also fits well with joint structures that involve much repeated movement. The Cycloidal gearbox can therefore be reviewed in a humanoid joint not as a simple reduction component but as a core drive component that raises power-transmission stability.
The Applicability of the Bonsystems Lineup to Humanoid Joints
Key Summary — Bonsystems develops reducer solutions applicable to robot joints and automation equipment based on cycloidal technology. Among these, the BSR is a component-level lineup that lowers rotation speed and transmits the needed force between the motor and the joint.
Bonsystems develops reducer solutions applicable to robot joints and automation equipment based on cycloidal technology. Among these, the BSR is a component-level lineup based on cycloidal reducers, playing the role of lowering rotation speed and transmitting the needed force between the motor and the joint. In structures where space is limited and repeated load changes occur, as in humanoid joints, the reducer’s size, power-transmission method, and internal-structure stability become important review elements.
Bonsystems’ reducer technology also connects with a compact structure, a Pinless design, and a design direction that reduces the part count. The Pinless structure aims to reduce some of the coupling elements once needed in conventional pin configurations and configure the reducer’s internal structure more simply. This design can help raise space utilization and ease of assembly in humanoid design, where the drive unit must be arranged within a confined joint space.
Humanoid joints are still a field where various structures and drive methods are reviewed together. Rather than asserting that a specific reducer applies identically to all joints, a process of examining the load, range of motion, motor specification, and profile conditions of each joint area together is therefore needed. Centered on the BSR cycloidal reducer, Bonsystems can review the reducer application direction needed for humanoid joints together, and, as needed, can also consult on the possibility of extension at the actuator level.
F.A.Q
Q: Why does reducer selection matter for humanoid joints?
A: The reducer plays an important role in converting the motor’s rotational force into the force needed at the joint and realizing stable movement within a confined space.
Q: What role does the Cycloidal gearbox play in humanoid joints?
A: With a wide tooth-contact area, it has the structural characteristic of distributing and transmitting force widely. It can be reviewed as a reduction method that helps stable power transmission in a joint environment where shock and load changes are repeated.
Q: Why does a slim structure matter in humanoid joints?
A: Inside a humanoid joint, the reducer, motor, sensor, wiring, and structural components go in together. When the reducer and actuator are designed thin and compact, it helps arrange the drive unit and surrounding components more efficiently within a confined space.
Q: In what way can the Pinless structure help?
A: The Pinless structure is a design direction that reduces some of the coupling elements once needed in conventional pin configurations and configures the reducer’s internal structure more simply. When the component composition is concise, it can help reduce the assembly and maintenance burden and raise the ease of design in confined joint spaces.
Q: What advantages can the Bonsystems reducer have in humanoid joints?
A: In humanoid joints, a reducer that stably converts the motor’s rotational force into the force needed for joint movement matters, because there are many motions with repeated load changes, such as walking, maintaining balance, and object manipulation. The Bonsystems BSR is a reducer lineup that distributes and transmits force widely based on a cycloidal reduction structure, and can be reviewed in robot designs that must configure a stable drive unit within a confined joint space.
