JPH04213707A - Angular positioning device - Google Patents

Abstract

PURPOSE:To execute the positioning with high accuracy by attaching a rotary encoder of high accuracy to a motor shaft, and providing a digital signal processor(DSP) and a processor for managing it. CONSTITUTION:An output signal of a rotary encoder 4 is multiplied through a multiplying equipment 10, and counted by a counter 9. This count data is sent to a DSP 6 and utilized as position data. Subsequently, in the DSP 6, based on the position data of the counter 9, a moving amount of a motor 3 is subjected to arithmetic processing, and it is sent to a D/A converter 7 as digital data of a current value required for driving the motor 3. Its data is converted to analog data which can drive the motor 3 therein, and subsequently, converted to a current being sufficient for driving the motor 3 by a linear servo-driver being a motor driver 8. In this regard, as for the motor 3, a three-phase brushless motor is used.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular positioning device capable of performing precise minute positioning.

0002

2. Description of the Related Art Conventionally, precision micro-positioning devices often use a laser interferometer, and in this device, a laser beam of a gas laser is routed and a plurality of expensive optical devices are arranged.

0003

[Problem to be Solved by the Invention] The laser interferometer method described above has a wide layout because it arranges a gas laser oscillator, an interferometer, optical elements such as a corner cube, and equipment, and circulates a laser beam between them. Space is required. Furthermore, since it uses an interferometer, its characteristics may fluctuate due to temperature fluctuations, airflow fluctuations, etc., so it must be used in a clean room.

[0004] Because of the above-mentioned major constraints, ie, constraints on space and use environment, the laser interferometer method results in a very high cost.

[0005]

[Means for Solving the Problems (and Effects)] According to the present invention, by attaching a high-precision rotary encoder to the motor shaft, it is possible to eliminate the adverse effect of the coupling on high-precision positioning. A positioning actuator with a resolution corresponding to a high-precision position sensor can be obtained.

Furthermore, this actuator is equipped with a digital controller centered on a digital signal processor, and a motor driver that includes P, which can be a source of noise.
By using a linear driver instead of a WM type, the oscillation effect caused by switching can be reduced.
Positioning can be done in a short time. (Oscillation makes positioning difficult and takes a long time to settle.)

[0007]

[Example] An example will be described with reference to the drawings. FIG. 1 is a diagram showing an example in which the present invention is applied to a track writing device for a hard disk. In the figure, 7 is a track writing head of the hard disk drive. 1
is a brushless motor that drives the head. 2 is a linear driver that drives the brushless motor. 5 is a rotary encoder that detects the rotation angle of the brushless motor and converts it into a digital signal. Reference numeral 3 denotes a DSP (digital signal processor) that digitally calculates command input values and current position and speed information from the rotary encoder according to a preset program, and creates commands to be given to the brushless motor. A D/4 converts the digital output signal of the DSP 3 into an analog signal input to the linear motor driver 2.
It is an A converter. 6 is a host CPU. Add further explanation.

1 is a user's host computer;
Through this, the controller 2 of the angle positioning device in this case
The operator gives commands to the This is called remote mode. In addition, there is a mode called "manual mode" in which 1) inching and other inching is performed without using a host computer and 2) by using multiple key switches 13 on the front panel of the controller (not shown). be. 1
1. The display device displays the amount of rotation of the motor 3 and the rotary encoder 4 having a common axis with the motor 3 as a 7-digit numerical value. When the rotation direction is CCW (negative direction) when viewed from the motor shaft,
A (-) sign is also displayed. (No sign in the positive direction).

[0009] The displayed value is Z of rotary encoder 4.
Either a mechanical coordinate system based on the phase signal or a program coordinate system in which an arbitrary offset is set from the mechanical coordinate system are displayed. (That is, the program coordinate value=machine coordinate value+offset amount).

Regarding the lamp 12 (see front panel layout diagram 1b). The meanings of the various lamps installed on the panel are as follows. 1. Servo ON When lit, it indicates that the servo system is powered on. 2. Synchronization (SYNC) Lights up when the machine coordinate system is established. When this lamp is not lit, all operations involving axis movement other than home return cannot be performed. 3. Alarm Indicates that the system has detected some abnormality. The alarm contents can be obtained through the host. 4. In-position (Inpos) Lights up when the servo system reaches the commanded target position.

Regarding the key switch 13 (see front panel layout diagram 1b).

[0012] The meanings of the various key switches installed on the panel are as follows. 1. Servo on switch When the servo is off, press this switch to turn the servo on. The servo on lamp will light up. This switch is momentary and is only active while it is pressed. When turning on the servo power, press this switch until the servo on lamp lights up. 2. Emergency stop switch When this switch is set to the ON position, the lamp attached to this switch will light up, the system will enter an emergency stop state, the servo will turn off, and the servo on lamp will go out. When this switch is in the ON position (when the lamp is lit), the servo will not turn on even if you press the servo on switch described in the previous section. When turning on the servo, turn this emergency stop switch to the OFF (lamp off) position. This switch is a toggle type; press it once to turn it on, press it again to turn it off. This switch is valid at any time regardless of the operating mode or operating state. 3. Mode selector switch This system has manual mode and remote mode.
It has two driving modes. The mode changeover switch is used to change between these two modes. Also,
In remote mode, you can select either RS232C or RS422 communication method. The mode selector switch is also used to select this communication method. When the mode selector switch is set to RS232C or RS422, it automatically becomes remote mode. 4. Homing switch This switch is only active in manual mode. Pressing this switch in manual mode moves the motor to the origin of the machine coordinate system. If you press this switch immediately after turning on the power, the Z-phase detection operation of the detector will also be performed at the same time. This switch is momentary type. 5. CW, CCW switch This switch is valid only in manual mode. While the CW switch is pressed, the motor continues to rotate at a constant speed in the CW (clockwise) direction as viewed from the motor shaft side. When you press the CCW switch, the motor rotates in the opposite direction (counterclockwise) to the CW switch. 6. RESET switch Performs a hardware reset. The system will be in the same state as when it was powered on.

Next, the operation modes ("manual mode" and "remote mode") will be explained.

(Manual mode) In manual mode, the positioner can be operated by itself using the key switch on the panel without using a communication line. The following describes typical operating procedures in this mode.

(Operating procedure) 1. Turn the mode selector switch to the MANUAL position,
Select manual mode. 2. Press the servo on switch to turn on the servo power. At this time, the servo on lamp lights up, indicating that the servo system is powered on. 3. Press the home return switch. The motor automatically moves to the machine home position. At this time, the synchronization lamp (SYNC)
lights up to indicate that the machine coordinate system has been established. 4. Rotate the motor to any position by pressing the CW or CCW switch. Depending on the motor rotation angle, the display will display the number of pulses corresponding to the motor rotation angle.

(Remote Mode) Remote mode is a mode in which the positioner operates according to commands from the host via communication. Either RS232C or RS422 can be selected as the communication method. Remote mode is automatically selected by selecting RS232C or RS422 with the mode selector switch on the panel.

(Communication Means) The communication method that can be used with this system is RS232C or R.
It is either S422. Communication uses only the data line and ground line, and no other control signals are used.

(Command Format) This section explains the theoretical specifications (protocol) of communication. Commands from the host to the positioner are executed by transferring ASC11 character strings. The general format of command data is shown in the figure below.

[0019]

[Outside]

(1) Command classification ASC11-1 indicating the major classification of commands
It's a character. C: Condo P: Parameter S: Reply to host (2) Command ID A numerical value (hexadecimal number) indicating the subclassification of the command. (3) Data Data used as arguments for commands.

Specifically, the contents of the command are as follows.

[0021]

[Outside]

Returns the system to its initial power-up state. The system state is initialized to the following mode. Axis synchronization is not lost. 1. Coordinate system: Machine coordinate system 2. Position command method: Incremental type 3. Acceleration/deceleration: None

[0022]

[Out] Temporarily clears the alarm (error) that occurred in the system. However, if the cause of the alarm is not cleared, the alarm will be set again.

[0023]

[Outside]

The operation is the same as pressing the home return switch in manual mode.

[0024]

[Outside]

Commands servo ON/OFF. To turn on the servo, set the data to “1”, to turn it off, set “1” to the data.
0". When the servo is turned on, the servo on lamp on the panel lights up and the motor becomes servo locked.

[0025]

[Outside]

Resets servo amplifier errors (overcurrent, overload).

[0026]

[Outside]

When the target speed and target position are set with the servo ON (servo ON lamp lit) and return to origin completed (SYNC lamp lit) and this command is sent from the host, the motor will move to the target position. During movement, the in-position lamp turns off, and when the motor reaches the target position, the in-position lamp turns on.

[0027]

[Outside]

If this stop command is issued while the motor is rotating due to the above start command, the motor will stop at the position where the stop command was received without reaching the target position.

[0028]

[Outside]

This command is valid only when the return to origin is completed and the motor is not rotating. When this command is received with the data set to "1", the positioner will set the coordinates currently displayed on the display as the origin on the program. The coordinate system set in this way is called program coordinates. Additionally, the unique coordinate system fixed to the motor is called the machine coordinate system. The machine coordinate system is established during the homing operation. If you set the data to "1" using this command (CC), it will become the program coordinate system, and if you set the data to "0", it will return to the machine coordinate system. The mode in which the system operates in the program coordinate system is called program coordinate mode, and the mode in which the system operates in the machine coordinate system is called machine coordinate system mode.

[0029]

[Outside]

Decide how to interpret the position data given by C14's target position. There are two position command methods: absolute coordinate command (absolute type) and relative coordinate command (incremental type).
There are different types. Absolute coordinate command is a method of commanding the offset from the origin of the machine coordinate system (or program coordinate system). On the other hand, relative coordinate commands are a method of commanding an offset from the current point, regardless of the machine coordinate system or program coordinate system. If you set the data to “0” with this command (C10), the absolute coordinate mode will be activated and the data will be set to “1”.
When commanded as , it becomes relative coordinate mode. This mode remains valid until C10 is commanded again. Also, if you command reset (C0), it will become relative coordinate mode.

[0030]

[Outside]

Instructs whether to perform acceleration/deceleration in response to a movement command. If the data is set to “0” and this command is issued, acceleration/deceleration will not be performed. If you set the data to “1” and issue this command, acceleration/deceleration will be performed. The acceleration/deceleration method can be changed using the parameter (PE).

[0031]

[Outside]

Command the target position given to the servo system using the number of pulses. Data is given in decimal numbers. The meaning of the data differs depending on the absolute coordinate mode/relative coordinate mode (C10).

[0032]

[Outside]

Commands the target speed given to the servo system in pulses per second. Data is given in decimal numbers.

[0033]

[Outside]

[0034]

[Outside]

Returns the current state of the system in hexadecimal. When each bit of status information is “1”, it has the following meaning.

[0035]

[Outside]

The actual alarm contents are confirmed by the operator in the next "system alarm request".

[0036]

[Outside]

16 abnormalities (alarms) currently occurring in the system
Returns as a base number. When each bit in alarm information is “1”, it has the following meaning.

[0037]

[Outside]

Next, the operating procedure when operating in remote mode will be described.

(Remote operation procedure) 1) Connect the communication cable to the RS232C (or RS422) connector on the front of the panel and connect it to the host side. 2) Set the mode selector switch to RS232C (or RS42
Turn to position 2) to select remote operation mode. 3) Bring the host side into startup state. 4) Send the command explained in the previous section to the positioner from the host side to perform remote operation.

(Programming method on the host side) When performing remote operation with this system, the host side always takes the initiative in communication. For example, when performing servo ON processing, the procedure is as follows.

[0041]

[Outside]

[0042] Whether a command is being executed or not is determined by checking the BUSY bit of the status information. Most commands are executed immediately when the command is sent, but the next process requires checking the BUSY bit or SRVON bit and waiting for the command to finish.

[0043]

[Outside]

In the above command, if the next command is sent to the positioner without confirming the completion of the command, a status error will occur and the command will not be executed. On the other hand, commands that request the following three positioner states are valid at any time.

[0044]

[Outside]

[0045] The user operates the host using the above method.

Next, the functions of each block of the controller 2 will be explained using the overall configuration diagram of FIG.

As mentioned above, various parameters are input to the serial I/O port (RS232) using the host computer.
C, etc.), and various output signals depending on the situation are sent from the controller 2 side by the action of the management CPU 5. In addition, the functions of the CPU 5 include I/O control of 11 displays, 12 lamps, 13 key switches, etc., and control of communication functions. The function of the CPU 5 is based on the memory 1 backed up by the battery 16.
Supported by 4.

Similarly, the function of the DSP 6 is based on the dedicated memory 1.
A data bus line 17 runs between the CPU 5 supported by the CPU 5 and the DSP 6, and data is exchanged.

The CPU 5 and the motor driver 8 are connected mainly through an I/O signal line for management related to overheating. The output signal of the rotary encoder 4 is multiplied by 40 through a multiplier 10, and then the number of pulses is counted by a counter 9. Real-time count data is sent to the DSP 6 and used as position data. Note that the Z-phase signal (origin) from the rotary encoder 4 is similarly input to the multiplier 10 and the counter 9, but it is not multiplied and is used as it is in the counter 9 as a reset pulse for the counter. be done. The DSP 6 calculates the amount of movement of the motor 3 in real time based on the output data of the counter 9, that is, the position data, and sends it to the D/A converter 7 as digital data of the current value necessary to drive the motor 3. send. Here, we convert it to analog data that can drive the motor,
Next, a linear servo driver called a motor driver 8 converts the current into enough current to drive the motor 3. Here, since the motor 3 uses a 3-phase brushless motor, the D/A converter 7 and the motor driver 8 are required for each of the 3 phases U, V, and W, that is, 3 sets (3 sets are required for the number of phases). ).

Next, the above operation will be explained.

First, the operating conditions for writing tracks on the hard disk (track spacing, etc.) are specified to the host CPU 6, and the host CPU uses the specified operating conditions to the DSP 3.
to communicate.

[0052] DSP3 is an incremental encoder 5
The current position signal of the writing head 7 (rotor of the brushless motor 1) is created by counting the digital output signal from the , the difference between this and the designated target position is calculated as the amount of movement, and the speed corresponding to this amount of movement is calculated. The command is output to the D/A converter 4.

Furthermore, in order to detect the origin position and determine the direction of the incremental encoder 5, and to perform minute positioning of the writing head, the output pulses of the encoder are divided,
Performs calculations to increase resolution.

Further, the amount of movement is calculated from the difference between the current position signal and the designated target position signal, and a speed command is created according to a predetermined correspondence rule. When high-accuracy and high-speed positioning is desired, the correspondence rule may have to be nonlinear.

For example, the amount of movement and the speed command as shown in FIG. 4 are made to correspond nonlinearly. The motor drive signal converted into an analog signal by the D/A converter 4 is power amplified by the linear motor driver 2, drives the brushless motor 1, and causes the write head 7 to perform a predetermined operation.

Here, since the motor driver 2 is of a linear type, noise generation is extremely small and linearity is maintained in the minute displacement region, making highly accurate control possible. Further, since the write head 7 has a high impedance and is easily susceptible to noise, a linear type motor driver 2 that generates extremely little noise is required. The brushless motor 1 also has no mechanical sliding parts, so it generates less electrical and mechanical noise and has good controllability.

The above embodiment will be further explained.

FIG. 3 is a further block diagram of the controller. In the figure, DSP is a digital signal processor, which is used here to calculate the control amount for servo control. FIG. 4 shows a further block diagram of the digital signal processor DSP. As shown in the figure, address switches ADDS, address processing units AALU and X for address calculation are connected via an address bus for sending and receiving addresses from the outside.
and memories MEMX and MEMY for Y addresses, memory MEMP for programs, data bus switches DBSE and DBSI connected to internal and external data buses, processing unit ALU for data processing, controller CONT that accepts clocks and interrupts, and connections with peripherals. It has a peripheral circuit PI etc. for measuring. Returning to FIG. 3, MEMD is a fast-accessible memory into which programs to be executed by the digital signal processor DSP are loaded.

The CPU is a processor that manages the controller and causes the digital signal processor DSP to perform calculations. MEMC is a program memory that stores programs to be executed by the processor DSP and CPU, respectively. The processing procedure of each program is shown in Figure 7.
- shown in FIG. 14. The program of the processor DSP is transferred from the memory ROM to the processor CPU processor DS.
is loaded into the memory MEMD via P and the processor D
Executed in SP. By doing this, processor D
SP execution processing becomes faster. RAM is a memory that temporarily stores processing data, status data, etc. ADD
DE is an address decoder that transmits instructions from the input port to the processor DSP and CPU. DP is a display circuit,
Display internal information and status. CNT is a counter that receives the signal from the encoder and sends it to the DSP. MD is a motor driver that transmits the output from the processor DSP to the brushless motor.

[0060] IF is an interface, and the processor CP
Realizes communication between U and an external host computer.

Details of the aforementioned counter are shown in FIG. IN is an input section that receives the signal from the encoder and
It determines the phase direction and pulse and generates each signal. G is a gate that controls the Z-phase signal. CNT is a counter that receives a signal from the input section IN, counts up and counts down, and is cleared (initial value) by a signal from the gate G.

SM is a shift register, which converts the output of the counter into parallel and serial data and sends it to the processor DSP. Note that since the gate G is opened and closed by a program command from the DSP, the Z-phase signal is used to clear the counter when necessary.

FIG. 6 is a detailed diagram of the motor driver MD, which divides data from the processor DSP into three phases into U, V, and W phases and sends drive signals to the motor. In the figure, DA is a digital-to-analog converter, and the analog signal is amplified by a driver and applied to the motor. SW is a switch,
It is configured to turn from ON to OFF in response to commands such as overheat, overload, and emergency stop.

[0064] Startup is performed with power O to the processor CPU.
N or a command from the host computer, the processor DS in the program in the memory ROM
A program for P is loaded into the memory RAMD through communication between the processor DSP and CPU, and when the program is finished, the processor CPU and DSP enter a waiting state for processing.

First, the processor CPU determines whether the mode is remote mode or manual mode, as shown in FIG. 7, and executes each process. The remote mode is activated by instructions from the host computer, and the manual mode is activated by the manual switch on the controller.

In the remote mode, processing is performed as shown in FIG.

The processor CPU executes processing as follows. If there is input information from the host, the process moves to the next step, analyzes the input information, and outputs data to the processor DSP.

Next, wait for a response from the processor DSP,
If there is input information from the processor DSP, the information is sent to the numerical display circuit DP for display, and the data is sent to the host computer either directly or after being processed, and the process returns to the beginning.

If the mode is the manual mode, it is checked whether the manual switch SW has been operated, and if so, the input key is analyzed, information is sent to the processor DSP, and a response from the processor DSP is awaited. If there is information from the processor DSP, it is sent to the display circuit DP and displayed, and the process returns to the beginning.

Next, the operation of the processor DSP will be explained.

As shown in FIG. 10, processing is performed to initialize the inside of the processor DSP and check internal flags. In such a state, if an interrupt is received at the interrupt port, interrupt processing starts as shown in FIG. Here, processing for receiving data from the processor CPU, processing for motor control, processing for transferring data to the motor driver, and processing for receiving data from the counter are performed. The reason for doing this is to execute the process on time.

Next, flag check processing will be explained as shown in FIG.

First, it is checked whether there is a servo-on command, if not, whether the control has ended, and if so, whether the control has started. If NO, initialize the control and
Move on to the next step. It is determined whether there is an origin movement command, and if there is, the controlled object is moved to the origin. Next, check whether there is a start command (target position), and if so, start the controlled object. If the target position has been reached, the movement is stopped and the process is ended.

Next, motor control processing will be explained with reference to FIG. 13.

First, it is determined whether ZPhase has been detected, and if NO, the process ends; if YES, the following process continues.

The contents of the register are saved and the current position information is read from the counter.

Next, the current loop calculation is performed. Then, it looks at the value of the built-in counter, determines whether it is a velocity loop or a position loop, and executes the respective calculation process.

Next, it is checked whether there is a target value (reference), and if there is, it is used; if not, it is generated and the next process is executed.

Next, the state is checked, the built-in counter is counted up, the saved value is returned to the register, and the process ends.

The above-mentioned state checking process will be further explained with reference to FIG. 14.

First, it is determined whether the stroke has exceeded. This means that if the rotation angle of the motor exceeds or is about to exceed the limit in the positive or negative direction set by the parameter, it will be considered to have exceeded the limit. Set, clear the busy status, and end the process.

On the other hand, if it is not over, then it is determined whether or not it is at the target position. If there is, it is set to indicate that it is at the target position, and if it is not, the status indicating that it is at the target position is cleared.

Next, check whether the position error is too large,
If NO, it is checked whether the target position has been reached within the set time, and if it is not overtime, the process is ended. If the position error is too large or the time is over, the counter is set to overflow or in-position overtime, a stop command is set, the busy status is cleared, and the status check ends.

(Other Embodiments) As a second embodiment, the D/A converter 7 in FIG. 1 is required for the number of phases of the motor as described above, but the
If digital data for each phase is sent, the number of data sent to the D/A converter 7 will be reduced due to data bus line restrictions, and as a result, it will be difficult to drive the motor 3 with high resolution. As shown, DSP6 and phase number D/A
A multiplexer 17 is installed between the converters 7 in an attempt to eliminate the above-mentioned restrictions.

[0085]

[Effects of the invention] Highly accurate positioning is possible without the need for large spaces or air conditioning (including temperature) and airflow management, which were conventionally required, so the total cost per unit is significantly reduced. . Therefore, it is possible to reduce the cost of products produced using it. As hard disk drives become more dense, servo track writing becomes more precise.
High resolution is now required, but if you use such an external precision positioning device (rather than the hard disk drive's own drive actuator) to write a servo track that serves as a high precision reference, it will be possible to improve the head of the product. Since the actuator does not need to have such high precision, it becomes easy to improve the precision of the hard disk drive.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to a hard disk writing device.

FIG. 2 is a diagram showing a front panel.

FIG. 3 is a block diagram of a controller including a CPU and a DSP.

FIG. 4 is a block diagram of a DSP.

FIG. 5 is a block diagram of a counter.

FIG. 6 is a block diagram of a motor driver.

FIG. 7 is a diagram showing a CPU control procedure.

FIG. 8 is a diagram showing a CPU control procedure.

FIG. 9 is a diagram showing a CPU control procedure.

FIG. 10 is a diagram showing a DSP control procedure.

FIG. 11 is a diagram showing a DSP control procedure.

FIG. 12 is a diagram showing a DSP control procedure.

FIG. 13 is a diagram showing a DSP control procedure.

FIG. 14 is a diagram showing a DSP control procedure.

FIG. 15 is a block diagram showing another embodiment.

[Explanation of symbols]

1 Host computer 5 Processor CPU 6 Processor DSP 4 Rotary encoder

Claims (2)

[Claims] Claim 1: An encoder motor in which a rotating shaft of a rotary encoder and a rotor of a motor are coaxially integrated, a multiplier of the encoder, and a counter that counts the output from the multiplier and outputs it in real time. , a digital signal processor that calculates and controls the amount of rotation of the motor according to the counter output, and a plurality of D/D converters corresponding to the number of phases of the brushless motor that converts the digital data output from the digital signal processor into analog data. An angular positioning device consisting of an A converter, the same number of motor drivers, and a management microprocessor that controls the entire operation sequence. 2. The positioning device according to claim 1, wherein a linear driver is used as the motor driver to reduce vibration during settling of precise positioning.