Die Cushion Press Control with Torque Feedback and Dynamic Speed Compensation
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Solution Overview
Problem
Existing die cushion press control systems fail to meet the dynamic control requirements of modern forming processes due to inadequate management of motor torque changes caused by acceleration, braking, friction, and motor losses, leading to suboptimal control quality and dynamics.
Innovation Solution
A device and method that adjust motor speed based on target speed, incorporating feedback from current and speed sensors to automatically account for acceleration and loss components, allowing smooth transitions between position and force control modes, and using existing sensors to enhance control dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure control system outputs motor torque based on die cushion pressure command, then pressure control is achieved, but motor torque is subject to very strong changes due to acceleration, friction, and motor losses
Solution Approach 1:
The patent implements a feedback mechanism where the actual motor torque is measured and compared with the commanded torque. The difference is compensated by adjusting the pressure command to the hydraulic pump, ensuring stable motor operation while maintaining precise pressure control. This resolves the contradiction by using feedback to decouple the pressure control from direct motor torque variations.
Solution Approach 2:
The patent introduces an intermediary pressure control mechanism between the motor and the die cushion. Instead of directly controlling motor torque to achieve pressure control, the system uses pressure sensors and a pressure command adjustment mechanism as intermediaries. This intermediary layer filters out the direct impact of motor torque variations, resolving the contradiction between pressure control precision and motor torque stability.
2Manufacturing precision
If motor torque is controlled based on die cushion pressure, then pressure control is achieved, but control dynamics do not meet requirements of modern forming processes
Solution Approach 1:
The patent uses feedback from pressure sensors to continuously adjust the pressure command, enabling dynamic adaptation to process requirements. This feedback mechanism allows the system to respond quickly to changes while maintaining precise pressure control, resolving the contradiction between control precision and control speed.
Solution Approach 2:
The patent implements dynamic pressure command adjustment based on actual process conditions. The pressure command is not fixed but is continuously modified according to feedback from pressure sensors and the state of the forming process. This dynamic approach enables the system to meet the fast response requirements of modern forming processes while maintaining precise pressure control.
3Device complexity
If acceleration and loss components are not commanded to the electric motor, then control system is simpler, but motor torque requires strong changes to compensate for losses
Solution Approach 1:
The patent uses feedback to automatically compensate for acceleration and loss components without requiring complex feedforward calculations. The pressure sensor feedback provides information about the actual system state, allowing the control system to adjust the pressure command to account for motor losses and acceleration effects. This resolves the contradiction by using simple feedback instead of complex feedforward control.
Solution Approach 2:
The patent enables the control system to self-compensate for motor losses and acceleration effects through pressure feedback. The system automatically adjusts the pressure command based on the actual pressure and motor state, without requiring external intervention or complex pre-calculation of loss components. This self-service mechanism maintains motor torque stability while keeping the control system relatively simple.
Data Source
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AI summary
The invention relates to a device and a method for open-open or closed-loop control of a movement of a die cushion of a die cushion press. The device has an control value encoder (11), a speed controller (12), a current controller (13) and a motor control device (14) for providing a nominal current for an electrical drive (15) of a fluid-hydraulic motor pump unit (20) for moving a die cushion of a die cushion press. The control value encoder (11) is provided in order to calculate a setpoint speed based on a die cushion control value command and a piece of die cushion information. The speed controller (12) calculates a setpoint current based on the setpoint speed. The current controller (13) calculates a control signal based on the setpoint current, and the motor control device (14) calculates the nominal current based on the control current. According to the invention, the dynamics of the control of the electrical machine can thus be improved.