Door Controller can be roughly divided into two methods - open loop and closed loop control methods, which are used with different door opener structures.
Open Loop Control
The so-called open loop control means that the motor is not equipped with a speed feedback device (Feed Back Device). The controller is only responsible for providing a fixed voltage to the motor without any speed compensation. In the past, when control electronic technology was less developed, it was more difficult to control the acceleration and deceleration of the motor. In order to achieve rapid and smooth acceleration and deceleration when opening and closing the door, a linkage group mechanical structure was used to generate a similar sine wave acceleration and deceleration to achieve a comfortable door opening and closing action.
There are roughly two types of motor control technologies currently in use:
1) DC motor
2) Three-phase AC induction motor
Comparison table of various features:
Motor cost Controller cost Motor efficiency Operating characteristics
DC motor High Low 70~80% better
Three-phase AC induction motor Low High 60~70% Poor
Closed Loop Control
Closed-loop control refers to the speed and position feedback components of the motor device. If the speed control adjustment rate is required to be below 0.01%, the motor must be equipped with a TG (Tacho Generator) and a PG (Encoder) for position feedback. Currently, PG is mostly used as a component for both speed and position feedback. It has the ability to automatically adjust to the door width, making construction adjustments easy and reducing defective rates. Due to the advancement of control technology, the structure of the door opener has been simplified, the complex linkage mechanism has been omitted and the timing belt directly drives the door panel, and the cost of the mechanical structure has been reduced.
There are roughly 3 types of control techniques currently in use
(1) Permanent Magnet DC Motor─ PM DC Motor This control method is one of the most traditional control methods. Its advantages are simple control principle, low failure rate, not easy to generate electromagnetic interference, low cost, and smooth operation at low speed. Motor efficiency The disadvantage is that the motor system uses Mechanical Commutation, and the carbon brushes will cause wear and noise. However, as long as the motor is properly designed and manufactured, it can be used for 15 years in the application of the elevator door without having to replace the carbon brushes. The noise value can be controlled below 50db.
(2) Induction AC Motor─ IM AC Motor The advantage of this control method is that the motor structure is simple, so the cost is low and durable. With the continuous improvement of vector control (Vector Control) technology in recent years, significant improvements have been made in low-speed operation control and interference prevention. This technology has become increasingly mature in Taiwan.
(3) Permanent magnet AC (brushless DC) motor ─ PM AC (Brushless DC) Motor This is the latest and most advanced control technology. At present, most controllers have used DSP technology. There are roughly 2 kinds of input voltages - square wave and sine wave. Among them, the sine wave control method makes the motor have a relatively stable speed and efficiency at low speeds. The working principle of the motor is evolved from the permanent magnet DC motor.
Its advantage is that the motor has the highest efficiency and the smallest volume (about half of the induction AC motor). The motor adopts electronic commutation (Electronic Commutation), so there is no disadvantage of carbon brush and commutator wear and noise of DC brushed motor. Its advantages can be said to combine the advantages of permanent magnet DC motors and induction AC motors. The use of this technology abroad has become increasingly mature, and it has been successfully applied to hoist motors that are directly driven without a reducer. The only disadvantages are high technical threshold and high cost.
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