Die Cushion Press Control with Speed-Current Cascade Feedback
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Solution Overview
Problem
Existing die cushion press control systems fail to effectively manage motor torque variations due to inertia, friction, and motor losses, leading to suboptimal control quality and dynamics in modern forming processes.
Innovation Solution
A device comprising a control value encoder, speed controller, current controller, and motor control device that calculates a nominal current for an electrical drive of a fluid-hydraulic motor pump unit, allowing for improved control behavior by specifying a motor speed proportional to force or pressure increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open-loop control of electric motor torque is used based on die cushion pressure command, then the control structure is simple, but the control quality and dynamics do not meet modern forming process requirements due to strong variations in motor torque from friction and motor losses
Solution Approach 1:
The patent implements feedback control by measuring actual die cushion pressure and using it to adjust motor torque in real-time. The control system continuously monitors the pressure between the die cushion and workpiece, comparing it with the target pressure, and dynamically adjusts the motor torque to compensate for friction and losses, thereby achieving high control quality without excessive complexity
Solution Approach 2:
The patent replaces traditional mechanical linkage-based control with an electrical control system that directly adjusts motor torque. This substitution allows for precise, dynamic control of the die cushion pressure through electrical signals rather than mechanical mechanisms, improving control quality while maintaining reasonable system complexity
2Manufacturing precision
If motor torque is adjusted to compensate for friction and motor losses, then control quality improves, but motor torque becomes subject to very strong changes leading to poor control dynamics
Solution Approach 1:
The patent applies dynamics by making the control system adaptive and responsive to real-time conditions. The control algorithm dynamically adjusts motor torque based on actual pressure feedback, allowing the system to smoothly handle transitions between different operating phases (pre-acceleration, drawing operation, return movement) without abrupt torque changes, thereby maintaining both control quality and dynamics
Solution Approach 2:
The patent changes control parameters dynamically based on the operating phase. During pre-acceleration, position control is used; during the drawing operation, force control with velocity as disturbance variable is applied; during return movement, position control is resumed. This parameter adaptation allows the system to maintain optimal control quality and dynamics across different operating conditions
3Manufacturing precision
If position control is used during pre-acceleration and return movement, then positioning accuracy is achieved, but transition to force control during drawing operation requires complex controller switching
Solution Approach 1:
The patent implements a universal controller that can operate in multiple control modes (position control and force control) without requiring separate controllers for each phase. The same controller adapts its control strategy based on the operating phase, using position control for pre-acceleration and return movement, and force control with velocity feedback for the drawing operation, thereby achieving multi-functionality without increasing device complexity
4Manufacturing precision
If velocity of die cushion is used as disturbance variable in force control, then force control quality improves, but velocity measurement and integration into control circuit increases system complexity
Solution Approach 1:
The patent applies self-service by using the velocity of the die cushion, which is already known from the drawing operation requirements, as a disturbance variable in the force control. The system leverages existing velocity information without requiring additional complex measurement systems, thereby improving force control quality while minimizing increases in system complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the dynamic control quality of the die cushion press, enabling it to follow desired compression or force profiles during drawing operations, while independently correcting acceleration and loss components, thus improving the overall control quality and reducing disturbances.
Implementation Method 1
electrical drive (15) of a fluid-hydraulic motor pump unit (20)
Implementation Method 2
fluid-hydraulic motor pump unit (20) for moving a die cushion
Data Source
AI summary
In summary, the invention relates to a device and method for open-loop or closed-loop control of a movement of a die cushion of a die cushion press. The device has a 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 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. In this respect, the dynamics of the control of the electrical machine can be improved.