Buffer Motor Speed Control After Emergency Stop Release
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Solution Overview
Problem
Existing industrial machines face inefficiencies due to prolonged coasting of buffer motors without dynamic brake modules during emergency stops, leading to significant wait times and excessive regenerative power generation.
Innovation Solution
A controller determines the speed of a buffer motor at a predefined timing after emergency stop removal, using it as an initial speed to control the motor's acceleration to a base speed, thereby minimizing regenerative power generation and resuming operations quickly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the emergency stop is applied to the buffer motor without a dynamic brake module, then the device complexity is reduced, but the loss of time increases due to prolonged coasting
Solution Approach 1:
The controller stores the rotational speed of the buffer motor before emergency stop occurs. When emergency stop is removed, the controller uses this stored speed as initial speed for speed control, enabling immediate resumption of operation without waiting for the motor to coast to a stop. This preliminary storage of speed information resolves the contradiction by eliminating wait time without adding physical braking components.
2Productivity
If the emergency stop is removed while the buffer motor is coasting, then the productivity is improved by resuming operation quickly, but the use of energy increases due to large regenerative power generation
Solution Approach 1:
The controller continuously monitors the rotational speed of the buffer motor and uses this feedback to determine the appropriate initial speed for control after emergency stop removal. By basing the speed control on actual measured speed rather than assuming zero speed, the controller avoids commanding excessive acceleration that would generate large regenerative power, thus resolving the contradiction between quick resumption and energy efficiency.
Solution Approach 2:
The controller changes the parameter used for speed control from assuming zero initial speed to using the actual stored rotational speed. This parameter change allows the controller to calculate appropriate acceleration commands that minimize regenerative power generation while still enabling quick resumption of productivity.
3Loss of time
If the buffer motor is controlled to resume operation immediately after emergency stop removal, then the loss of time is reduced, but the stability of the system worsens due to rapid deceleration and regenerative power spikes
Solution Approach 1:
The controller stores the rotational speed information before emergency stop occurs, making this information available immediately when emergency stop is removed. This preliminary preparation allows the controller to instantly implement smooth acceleration from the actual speed rather than waiting or assuming zero speed, resolving the contradiction between quick resumption and system stability.
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
The controller enables rapid resumption of industrial machine operations without large power consumption by controlling the buffer motor's speed effectively, reducing wait times and power fluctuations.
Implementation Method 1
regenerative power in a motor is utilized... This other motor is decelerated at the timing of power consumption in the industrial machine. Consequently, regenerative power is generated from this other motor
Implementation Method 2
The DBM is configured to develop a short circuit between terminals of a servomotor via a resistor, so as to consume rotational energy as heat
Data Source
AI summary
This control device controls a buffer motor supplied with power from a power source that is shared with a drive motor driving an industrial machine, the control device comprising: a motor speed specifying unit that specifies the current speed of the buffer motor; an emergency stop detection unit that detects an emergency stop state; a buffer motor command generation unit that establishes, as an initial speed, the speed of the buffer motor at a prescribed timing after the detection of the release of the emergency stop by the emergency stop detection unit specified by the motor speed specifying unit, and generates a command for returning the speed of the buffer motor to a predetermined base speed at a predetermined prescribed acceleration; and a buffer motor control unit that controls the buffer motor on the basis of the command generated by the buffer motor command generation unit.