Stationary Ball Screw Servo Motor to Prevent Shaft Whipping
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Solution Overview
Problem
Conventional servo motors experience shaft whipping and resonance at critical speeds due to inertia, limiting their operational speed and stability, which can lead to system failure.
Innovation Solution
A servo motor system with a stationary ball screw design, where the motor housing translates along a fixed ball screw shaft, eliminating inertial loads and allowing for precise control of motion without whipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the servo motor operates at higher speeds to improve maneuvering efficiency, then the speed of end effector maneuvering is improved, but shaft whipping and resonance occur due to inertia
Solution Approach 1:
The patent inverts the conventional servo motor design by making the ball screw shaft stationary instead of rotating. The motor housing and rotor rotate around the stationary ball screw shaft, which is anchored to the housing. This inversion eliminates shaft whipping and resonance issues while enabling higher operational speeds up to five to ten times faster than conventional systems.
2Productivity
If the servo motor increases operational speed to improve productivity, then output per unit time is improved, but position overshoot and shaft whipping occur due to end effector inertia
Solution Approach 1:
By inverting the design to have a stationary ball screw shaft and rotating motor housing, the patent eliminates the inertial effects that cause position overshoot. The stationary shaft configuration allows for faster acceleration and deceleration without the whipping and resonance that would compromise positioning accuracy, thereby improving both productivity and precision.
3Speed
If the servo motor operates at critical speeds to improve maneuvering performance, then speed and efficiency are improved, but violent vibrations are transmitted to bearings causing potential failure
Solution Approach 1:
The patent eliminates critical speed vibrations by inverting the conventional design. The stationary ball screw shaft is anchored to the motor housing, preventing the violent transverse vibrations and resonance that occur in rotating shaft designs at critical speeds. This allows the motor to operate at high speeds without transmitting harmful vibrations to the bearings.
Data Source
AI summary
A servo motor system having a direct drive motor, a controller, an encoder and a ball screw nut. The system may include a direct drive motor and a controller communicatively coupled to the direct drive motor and configured to provide a control signal to the direct drive motor to control rotational motion. The system may further include an encoder coupled to the direct drive motor and the controller and configured to provide a feedback signal to the controller indictive of the rotational motion of the direct drive motor. The system may further include a rotatably attached ball screw nut coupled to a housing for the direct drive motor, the ball screw nut configured to engage a ball screw shaft such that rotational motion imparted by the direct drive motor causes the servo motor system to move about the ball screw shaft while the ball screw shaft remains stationary.