Harmonic gearbox

Harmonic Strain Wave Gear in RDrive Servos

The RDrive series features integrated harmonic gearboxes that use strain-wave gear technology. With the gear ratio of 1:100 and an almost-zero backlash, the technology enhances the performance of our servo motors. This gives you precise motion control and high-torque output.

Why a servo needs a gearbox

When used in a combination with a servo motor, a gearbox, also called a gearhead or a speed reducer, allows for the following:         

1. Increasing the robotic actuator torque.
2. Reducing the servo motor speed. 
3. Balancing out the motor inertia against that of the load.

The effects are due to the gears in the servo gearbox creating a gear ratio. Applying the gear ratio of 1:100 to a motor generating 2 N·m of torque results in the output torque of 200 N·m. Similarly, if a motor runs at 4,000 RPM, the same ratio will reduce the speed to 40 RPM.

An imbalance between the motor and load inertia negatively impacts the robotic joint's performance and increases operating costs. Matching the inertia values, also achieved through the gearhead ratio, helps to avoid excessive overshoot, optimize power consumption, and improve the settling time.

Geared servo motors are critical for applications such as industrial robotics and pick-and-place systems, that require high-torque low-speed output and superior accuracy of motion.

Harmonic gearing

There's a variety of available gearing technologies including but not limited to: spur, planetary, worm, harmonic, and cycloidal. Our RDrive servos use harmonic gearboxes that are based on strain-wave gearing that was invented in 1957 by C.W. Musser.

Since then, the technology has evolved to provide the following benefits:

1. Almost-zero backlash | Enhanced performance, improved positioning accuracy, and a long and maintenance-free service life of servo motors.
2. High gearhead ratio | Enables high-torque and low-speed output at smaller motor sizes. It is also possible to reconfigure the ratio without modifying the design or the size of the entire mechanism.
3. Compact size and low weight | Allows for reducing the robotic actuator footprint and thus saving space in your application.     

When we were integrating strain-wave gear technology into our servo motors, we got less than 0.3 arcmin backlash, achieving high precision of motion control. The gearhead ratio of 1:100 allows us to multiply the output torque value by 100 while still allowing for our servo motors remain compact and lightweight. 

Strain Wave Gearhead: Operating Principle

The video is given for reference only

Geared servo motors—the Power of Integration

Though it is possible to use a gearbox and a servo actuator without assembling them into a single unit, their integration allows for a simple design and implementation of motion control systems. In the RDrive geared servo, the drive and the gear mechanism are already matched to work together and require no separate design and integration procedures, thus reducing engineering costs.

The overall length of our geared servo is shorter than that of an assembly where a servo motor is detached from a gearbox. Moreover, integrated units eliminate the need for additional couplings, minimizing the risk of bearing failures due to misalignment.

By combining a servo motor with a gearing mechanism, we improved power management and use, allowing for a better, longer, and more powerful servo.