Harmonic drive:the core component of your robot arm.
1. The origin of harmonic drive
Harmonic drive products are mainly used in more than 20 industries and fields such as wind power, nuclear power, artificial intelligence, automated production lines, aviation, precision machine tools, elevators, lifting, forklifts, high-speed rail, medical care, lawn mowers, and scooters. Among them, the reducers used for industrial robots are mainly harmonic drive and RV gearbox, which are one of the key core components of the robot industry, accounting for as much as 40% of the overall cost of industrial robots.
- The structure of harmonic drive
Wave Generator
The Wave Generator of harmonic drive is comprised of a specially designed thin raced ball bearing that is fitted onto an elliptical hub. This serves as a high efficiency torque converter and is used as the input of harmonic drive and is connected to the motor shaft.
Flexspline
The Flexspline is a thin cylindrical cup made from alloy steel with external teeth on the open end of the cup. The Flexspline is radially compliant but torsionally is very stiff. When the Wave Generator in inserted into the Flexspline the gear takes on its elliptical shape. The Flexspline is used as the output and is connected to the output flange.
Circular Spline
The Circular Spline is a rigid ring with internal teeth. When harmonic drive is assembled it engages the teeth of the Flexspline across the major axis of the Wave Generator ellipse. The Circular Spline has two more teeth than the Flexspline and is fixed to the harmonic drive housing.
3,The work Principle of harmonic drive
Below is an exaggerated two-dimensional diagram demonstrating how the three gear elements engage and rotate.
The Flexspline is slightly smaller in diameter and has two fewer teeth than the Circular Spline. The elliptical shape of the Wave Generator causes the teeth of the Flexspline to engage the Circular Spline at two opposite regions across the major axis of the ellipse. For every 180 degree clockwise rotation of the Wave Generator the Flexspline teeth are advanced counterclockwise by one tooth in relation to the Circular Spline. Each complete clockwise rotation of the Wave Generator results in the Flexspline moving counter-clockwise by two teeth from its original position relative to the Circular Spline. Because the gear teeth are always fully engaged in a region along the major axis, harmonic drive have Zero Backlash.
