Servo Press Motor Control via Rotational Angle Torque Fluctuation
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Solution Overview
Problem
Press machines employing servo motors require large capacity power sources and drive circuits due to the inability to accumulate rotational energy, leading to increased size and power consumption, while those using flywheels face challenges in downsizing the motor and drive circuit.
Innovation Solution
A control apparatus that detects the rotational angle and torque fluctuations of the crank shaft, adjusting the motor's rotational speed to optimize energy application, thereby reducing the maximum motor torque and power consumption by increasing speed when torque is lower than a reference value and decreasing speed when torque is higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a flywheel is employed to accumulate rotational energy, then the motor capacity can be reduced, but the apparatus size increases due to the flywheel and clutch
Solution Approach 1:
The patent replaces the mechanical energy storage system (flywheel and clutch) with an electrical energy storage system (capacitor). The capacitor accumulates electrical energy during non-pressing phases and discharges it during pressing operations, eliminating the need for mechanical flywheel while achieving the same energy management objective.
Solution Approach 2:
The patent changes the state of energy storage from mechanical (rotational kinetic energy in flywheel) to electrical (electrical energy in capacitor). This parameter change allows energy to be stored and released without the physical constraints of mechanical components, reducing apparatus size while maintaining motor capacity optimization.
2Volume of stationary object
If a servo motor is employed without flywheel, then the apparatus size is reduced, but the motor and power source equipment must be set to large capacity
Solution Approach 1:
The capacitor performs preliminary energy accumulation during non-pressing phases when the press machine is not in operation or during idle periods. This advance energy storage allows the servo motor to operate at reduced capacity during actual pressing operations, as the capacitor supplements the power delivery during high-demand moments.
Solution Approach 2:
The capacitor acts as an intermediary energy buffer between the power source and the servo motor. It decouples the motor size from the peak power requirements by absorbing excess energy during low-demand periods and releasing it during high-demand pressing operations, allowing the use of smaller motors.
3Volume of stationary object
If a capacitor is used to accumulate electric energy, then the AC power supply equipment can be downsized, but the drive circuit size increases due to high current supply requirements
Solution Approach 1:
The system operates in periodic cycles: the capacitor charges during non-pressing phases and discharges during pressing phases. This periodic charge-discharge operation allows the drive circuit to manage current flow in controlled pulses rather than continuous high current, reducing the required drive circuit capacity while still meeting peak power demands.
Solution Approach 2:
The patent changes the temporal distribution of current supply from continuous high current to pulsed current with periodic charging and discharging. This parameter change in current delivery pattern reduces the peak current handling requirements of the drive circuit while maintaining the necessary power delivery capability through energy accumulation and release cycles.
Data Source
AI summary
A control apparatus of a press machine in which a motor performance torque is fluctuated in accordance with a rotational angle of the rotating body in the case of rotating the motor at a fixed instruction speed. The control apparatus includes an angle detecting apparatus detecting a rotational angle of the rotating body, a torque determining apparatus determining a necessary motor torque in correspondence to a characteristic of the press machine on the basis of a value of the rotational angle input from the angle detecting apparatus, and a speed adjusting apparatus increasing the rotational instruction speed of the motor to a value more than the fixed instruction speed, at the rotational angle of the rotating body in which the necessary motor torque becomes smaller than a predetermined motor torque reference value.