Machine Element Motion Guidance Using a Digital Path Model
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Solution Overview
Problem
Existing methods for guiding the movement of machine elements, such as machine tools, often result in reduced dynamics and increased production costs due to jerk limitations and vibration issues, which are not adequately addressed by current techniques like jerk limitation, cam disks, and linear setpoint variable guidance filters.
Innovation Solution
A method that involves specifying setpoint guidance variables and determining actual pilot or guidance variables using a digital path model simulating the dynamic behavior of the machine element and motor, parameterized by the total moment of inertia and poles and zeros of the mechanical system, allowing for improved control without expert knowledge and numerical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If jerk limitation is applied to reduce vibration, then manufacturing precision is improved, but productivity deteriorates due to reduced dynamics and slower movement
Solution Approach 1:
The patent transforms the rigid jerk limitation approach into a flexible parameter-based control system. By representing jerk limitation as a transfer function with adjustable parameters (gain, cutoff frequency, time constants), the system can dynamically adapt the level of jerk reduction based on the specific machining conditions, tool characteristics, and workpiece properties, thereby maintaining production accuracy without unnecessarily limiting dynamics
Solution Approach 2:
The invention introduces a dynamic filter that adapts its characteristics in real-time based on the actual movement conditions. The filter parameters are continuously adjusted according to the current velocity, acceleration, and machine state, allowing the system to provide strong jerk limitation when needed (during cutting operations) while maintaining higher dynamics during non-cutting movements or rapid positioning, thus resolving the contradiction between precision and productivity
2Manufacturing precision
If path velocity is reduced to comply with jerk limitations, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The dynamic filter allows the system to maintain higher velocities when the machining conditions permit, and only reduce velocity when actually needed for precision cutting operations. The filter continuously monitors the machine state and adjusts the jerk limitation level accordingly, minimizing unnecessary velocity reductions and associated time losses
Solution Approach 2:
The filter is designed to anticipate upcoming movement changes and pre-adjust the jerk limitation parameters before critical operations begin. By preparing the control parameters in advance based on the planned trajectory and known machining requirements, the system can smoothly transition between different velocity levels without abrupt changes that would waste time
3Manufacturing precision
If linear setpoint variable guidance filters are used to reduce vibration, then manufacturing precision is improved, but reliability deteriorates due to signal delay causing inaccuracies
Solution Approach 1:
The patent incorporates feedback mechanisms that use actual measured values (position, velocity, acceleration) from sensors to continuously update the filter parameters and compensate for any delays. By comparing the actual system response with the desired trajectory and adjusting the control signals in real-time, the system maintains accuracy despite the inherent processing delays in the filter
Solution Approach 2:
The filter compensates for its own delay by predicting future position and velocity values based on current trends and the planned trajectory. This predictive capability allows the system to issue control commands that account for the processing time, ensuring that the actual movement follows the desired path accurately without being degraded by the filter delay
Data Source
AI summary
The movement of a machine element of a machine that can be driven via a shaft with the aid of a motor can be guided by specifying a setpoint guidance variable describing a desired movement process of the machine element for the actuation of the motor and determining an actual pilot variable and/or an actual guidance variable from the setpoint guidance variable by subjecting the setpoint guidance variable to a digital path model which simulates the dynamic behavior of the machine element and the motor. The digital path model is parameterized by the total moment of inertia and the poles and zeros of the transfer function of the mechanical system consisting of motor, shaft and machine element.