JPH084386B2 - Positioning control method by voltage source inverter - Google Patents

Description

The present invention relates to a positioning control method using an AC electric motor driven by a voltage source inverter.

[Conventional technology]

In the conventional positioning control method of this type, in order to reduce the position movement time by the high speed control of the AC motor and prevent the rotation speed pulsation in the low speed region of the motor, the positioning control system including the inverter as a whole is described above. It is known to have a speed control loop (ASR), a current control loop (ACR), and a position control loop (APR) for an electric motor and use an electromagnetic braking mechanism together.

[Problems to be solved by the invention]

However, in the positioning control method in the above-mentioned conventional method, the circuit configuration of the entire control system is complicated due to the mixture of the control loops as described above, and the feedback amount detection for each speed, current and position for operating each control loop is detected. The installation of the vessel caused an increase in the size of the equipment. In view of this, it is an object of the present invention to provide a high-speed and high-accuracy positioning method by forming a positioning control system only with a position feedback system and using a DC braking system of an AC motor together.

[Means for solving problems]

The inverter output frequency reduction control relating to deceleration and stop of the operating AC motor of the positioning control system is performed by a deceleration mode having a specific time characteristic, a deceleration mode having a position deviation proportional amount as its target frequency, and the output frequency being zero. This is done by selecting the sections at a plurality of specific positions from the DC braking. That is, in a positioning control system that includes a voltage source inverter, an AC electric motor driven by the inverter, and a position detector that works in conjunction with the electric motor to detect the current position of a load displaced by the electric motor and does not have a speed control loop, The inverter is a rotational pulsation reduction type in a low speed operation range of its drive motor, and for output frequency control of the inverter during fixed position stop operation, reduction control is performed in accordance with a predetermined time characteristic together with a stop command, and then the above. Each time the load position passes a plurality of specific points that are set apart from the stop target position by a predetermined value, the load position is reduced between the passing point and the next specific point according to the specified time characteristics. If the load position reaches between the last point of the plurality of specific point sequences and the stop target position, the position between the two positions is controlled. Reduction control is performed by using a deviation proportional value as a target value of the output frequency, and after the load position reaches the stop target position, DC braking of the electric motor is performed to set the output frequency to zero to decelerate the electric motor and stop the target. It is characterized in that the stopped state is maintained at the position.

[Action]

Generally, in high-speed and high-accuracy positioning control using an operating motor, the deceleration control of the electric motor in the process of reaching the stop target position is performed continuously by associating with the position deviation between the load current position and the stop target position in the entire deceleration process. When the position deviation is large, the control is performed according to a predetermined time characteristic with a focus on high-speed shift, and when the deviation is small, the control shifts to the position deviation control with accuracy as the main point, and switching between the two controls is performed. May be performed at the specific value of the deviation. In the present invention for shifting the electric motor by controlling the output frequency of the inverter, the deceleration control of the optimum time characteristic within the constraint value on the acceleration with respect to the load is divided into appropriate stages for each specific value of the position deviation in the high speed transition section. In the section in which the position accuracy is the main purpose, deceleration is performed by the position deviation proportional control in which the proportional amount of the position deviation is the target value of the inverter output frequency. In this case, the inverter has a function of stabilizing the rotation of the drive motor in the low speed range, such as a magnetic flux control loop. Further, when the load reaches the stop target position, the output frequency of the inverter becomes zero and the operating motor is stopped by DC braking and holds the state, but if the stop position fluctuates due to some disturbance, the operation is immediately performed. By the position deviation proportional control, the return operation to the original stop target position is performed and the state is maintained at the predetermined stop target position.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an operation diagram of a control mode changeover switch. FIG. 1 shows an example of using a magnetic flux control type voltage source inverter. The output of the frequency setter 1 is input to the acceleration / deceleration time adjuster 2,
The output of the regulator 2 is applied to the magnetic flux command amplitude calculator 3 and the changeover switch SW ₂ . The calculator 3 and the output of the regulator ₂ via the switch SW ₂ are input to the magnetic flux command generator 4. The output of the command generator 4 gives a set value for the magnetic flux of the stator of the positioning operation induction motor 8, and the output of the controller 2 via the arithmetic unit 3 and the switch SW ₂ is fixed respectively. The amplitude and frequency of the child magnetic flux set value are designated. The magnetic flux setting value is compared with the output of the magnetic flux detector 7 which integrates the terminal voltage of the electric motor 8 to calculate the actual value of the stator magnetic flux. The difference between the set value and the actual value of the magnetic flux is input to the magnetic flux controller 5, the output of the controller 5 is input to the PWM inverter 6, and the output voltage of the inverter 6 fixes the electric motor 8 by the output voltage. The child magnetic flux is controlled to be equal to the magnetic flux set value. Next, the stop position command value selected by the stop position setting device 9 is input to the stop position setting input device 10. Further, the output position signal of the pulse encoder 16 which is interlocked with the electric motor 8 through the coupling 17 is input to the position detector 15,
The output of the detector 15 is compared with the output of the position setting input device 10, and the difference between the two outputs is input to the position adjuster 12. The output of the regulator 12 is input to the magnetic flux command generator 4 via the switches SW ₁ and SW ₂ as an output frequency designation signal of the inverter 6. The sequence processing unit 14 inputs the constant position stop mode command from the contact 11, the output of the time adjuster 2, the output of the position setting input device 10 and the output of the position detector 15, and is displaced by the electric motor 8. A desired sequence signal is output according to the positional relationship between the position of the load and the stop command position, that is, the stop target position, and the switches SW ₁ and SW ₂ are switched and driven by the output sequence signal. FIG. 1 shows two control mode switching points according to the positional relationship between the switches SW ₁ and SW ₂ , the stop target position and an intermediate set point set apart from the target position by a predetermined value. This is an example of the case where the position of the load approaches the stop target position, and the switches SW ₂ and SW ₁ are in the contact closed state when the intermediate set point and the stop target position are reached. The state shown in FIG. 1 is reversed. Therefore, when the contact 11 is closed and a fixed position stop mode command is issued and the positioning control system starts the stop operation by the output signal of the sequence processing unit 14 and the load position approaches the stop target position,
Until reaching the intermediate set point, the switches SW ₁ and SW ₂ are in the states as shown in FIG. 1, and the control system enters deceleration control according to a predetermined time characteristic designated by the time adjuster 2, and then the above-mentioned When the intermediate set point is passed, the switch SW ₂ is switched to the output side of the switch SW ₁ , while the switch SW ₁ itself does not change its state, the output of the position controller 12 is the switch SW 1.
Is added to the magnetic flux command generator 4 via ₁ and SW ₂ ,
The control system enters deceleration control in which the output frequency of the inverter 6 is reduced by position deviation proportional control with a target value being a proportional value of the position deviation between the current position of the load and its target position. Further, when the position deviation decreases and the load position reaches its target position, only the switch SW ₁ changes its connection state to issue a command to hold the load position at its target position. The frequency zero command which is connected to the output side and which is designated by the command unit 13 is applied to the magnetic flux command generator 4 via the switches SW ₁ and SW _2, and the output frequency of the inverter 6 becomes zero. The electric motor 8 enters a DC braking state and the load position is stopped and held at its target position. Next, the operation diagram of the switches SW ₁ and SW ₂ shown in FIG. 2 illustrates the load position and its stop target position by angles θ and θr, respectively. The figure (a) shows the change pattern of the deviation Δθ (Δθ = θr−θ) between the two angles with respect to the angle θ. ± Δθ ₁ is the angular deviation corresponding to the intermediate set point, and ± Δθ ₂ is the stop target. It is an angular deviation corresponding to the position θr, and is set to an optimum value depending on the control accuracy and the settling property. Figures (b) and (c) show the switch SW.
_The operation pattern corresponding to the angular deviation between ₁ and SW ₂ is shown, and the OFF state in the figure corresponds to the contact closed state shown in FIG.

〔The invention's effect〕

According to the present invention, in a positioning control system for driving an operating AC electric motor at a variable speed by an inverter, it is possible to reduce the rotational speed pulsation in the low speed region of the driving electric motor, such as a magnetic flux control type voltage inverter as the inverter. Further, the output frequency control of the inverter is performed by reduction control according to a predetermined time characteristic and position deviation proportional control, and DC braking is further used at a target position, and by switching and applying each at a predetermined specific position,
This enables high-speed and smooth deceleration and precise position retention, and simplifies the positioning control system by omitting the speed and current control loop for the electric motor.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an operation diagram of the control mode changeover switch in FIG. 1 ... Frequency setter, 2 ... Acceleration / deceleration time adjuster, 3 ...
Flux command amplitude calculator, 4 ... Flux command generator, 5 ... Flux controller, 6 ... PWM inverter, 7 ... Flux detector,
8 ... Induction motor, 9 ... Stop position setting device, 10 ... Stop position setting input device, 11 ... Fixed position stop mode command, 12 ...
Position adjuster, 13 …… Position hold commander, 14 …… Sequence processing unit, 15 …… Position detector, 16 …… Pulse encoder,
17 …… Coupling, SW ₁ , SW ₂ …… Switch.

Claims (1)

[Claims] 1. A voltage comprising a voltage source inverter, an AC electric motor driven by the inverter, and a position detector which is interlocked with the electric motor and detects a current position of a load displaced by the electric motor, and which has no speed control loop. In the positioning control method for a fixed-type inverter, the output frequency control of the inverter at the time of a fixed position stop operation is first reduced with a stop command in accordance with a predetermined time characteristic, and then the load position is set to a predetermined stop position from a predetermined stop position. Every time a plurality of specific points set apart by a value are passed, reduction control is performed between the passing point and a specific point located next to the point according to a predetermined time characteristic, and the load position is set to the plurality of points. If it reaches between the last point of the specific point sequence and the stop target position, the proportional value of the position deviation between the two positions is set as the target value of the output frequency. Reduction control is performed, and after the load position reaches the stop target position, DC braking of the electric motor is performed to set the output frequency to zero to decelerate the electric motor and maintain a stopped state at the stop target position. Positioning control method for a voltage source inverter.