ELECTROMECHANICAL ACTUATOR

Abstract: An electromechnical actuator comprises an electric motor 1, a control and drive circuit 2, 3 mounted integral with the electric motor 1, said control and drive circuit 2, 3 comprising a serial-to-parallel converter 12A for converting a control signal in the form of serial data 14A into parallel data, and mean responsive to the control signal in the form of parallel data for producing a drive current or voltage for the electric motor 1. A system for accessing or controlling by means of command from a main controller 13 to a plurality of actuators 11 having a control and drive circuit 2, 3 integral with the motor 1 itself is also disclosed.

Description: Field of the Invention The present invention relates to electromechanical actuators, and particularly such actuators combining an electric motor and a control and drive circuit for controlling the operation of the motor. Background of the invention Figure 1 shows an arrangement including a stepping motor 1, an example of electric motor, and a drive circuit 2 therefor. The drive circuit 2 comprises power transistors for switching on and off the electric current to the stator windings of the stepping motor 1. A timing control circuit 3 provides the drive circuit 2 with timing control signals to control the timings of the operation of the stepping motor 1. A controller 4 is in the form of a microprocessor (CPU) or the like and provides the timing control circuit 3 with control signals. The drive currents to the stepping motor 1 flow through output lines 5. Drive signal lines 6 and control signal lines 7 are also provided. V P and E P denote the power supply and the ground for the drive circuit 2. V L and E L denote the power supply and the ground for the timing control circuit 3. The controller 4 provides control signals of a specific mode, and in so doing commands the direction of rotation, i.e., single phase, two phase or signal/two phase, and the number of steps of the movement, to control the timing control circuit 3 following a specific procedure. The timing control circuit 3 responds to the commands and determines the phase to be excited and the driving time, and the over-drive time, in accordance with a pre-programmed drive procedure. The timing control circuit 3 continues to supply the drive signals 6 the commanded number has been completed. To keep the current supplied to the stepping motor 1 constant, a constant-current feedback is provided to control the on/off operation of the drive signals 6. The drive circuit 2 is responsive to the drive signals 6 and switches the power transistors provided to turn the drive current to each phase of the stepping motor 1 on and off. When an overdrive circuit is used, the current reference is switched to a larger value to produce larger torque. The stepping motor 1 generates torque by the interaction of the vector sum of the magnetic fields generated by the drive currents to the respective phases and the magnetic fields of the rotor magnets, and is accordingly controlled to rotate and stop. In a conventional arrangement, the controller 4, the timing control circuit 3 and the drive circuit 2 are mounted on a board separate from the stepping motor 1. Connecting wires or wiring boards are used for conducting drive current from the board on which the circuits are mounted, to the stepping motor 1. A large number of conductors are required between the board and the stepping motor, hindering reduction in size and cost. The conductors 5 between the board and the stepping motor can cause electromagnetic interference. For high power drives heat sinking must be provided on the board for heat dissipation again hindering size and cost reduction. When a number of stepping motors is to be driven separate conductors are needed for each of the motors giving rise to a large total number of conductors. FR-A-1543145 shows an electromechanical actuator which has circuitry associated with the motor of the actuator mounted with the motor in the motor assembly. Summary of the Invention According to the invention, there is provided an electromechanical actuator comprising an electric motor, and timing control and drive circuits mounted with the motor in the motor assembly, characterised in that the actuator comprises a serial-to-parallel converter in the assembly for converting into parallel data a control signal for commanding the required rotation of the motor produced in the form of serial data by a controller, the timing control circuit is responsive to the output from the serial-to-parallel converter for producing a drive signal for controlling the timing of the operation of the motor, the drive circuit is responsive to the drive signal for producing a drive current to the motor, the timing control circuit indicates the completion of the required rotation of the motor by producing parallel data, and the actuator further comprises a parallel to serial converter for converting the parallel data from the timing control circuit into serial data and sending the serial data to the controller. Drawings Figure 1 is a prior art arrangement for driving a stepping motor; Figure 2 is a block diagram showing an electromechanical actuator of the invention; Figure 3 is a diagram showing an example of a timing control circuit 3 and the drive circuit of the actuator of Figure 2; Figure 4a is a perspective view, partially broken away, of a motor assembly of the actuator of Figure 2; Figure 4b is a cross sectional view along line B-B in Figure 4a; Figure 5 is a block diagram showing a system including a plurality of motor assemblies and a single controller of an actuator system of the invention; Figure 6 is a schematic diagram of the serial data line interconnections in an actuator accessing system of another actuator system of this invention; Figure 7 is a block diagram of a motor control system for the embodiment of Figure 6; Figure 8 is a block diagram of a control section in the actuation system of Figure 6; Figure 9 is a flowchart showing the operation of the actuation system of Figure 6; Figure 10 is a diagram of the format of the serial data received by the actuator system of Figure 6; Figure 11 is a diagram of the format of the serial data sent by the actuator system of Figure 6; Figure 12 is a schematic diagram of the serial data line interconnections in another embodiment of this invention; Figure 13 is a flowchart showing the operation of the system of Figure 12; Figure 14 is a diagram of the format of the serial data sent in the embodiment of Figure 12; Figure 15 is a block diagram of the control section in yet another embodiment of the invention; Figures 16 and 17 are flowcharts showing the operation of the embodiment of Figure 15; Figure 18 is a block diagram of a motor device used in another embodiment of the invention; Figure 19 is a flowchart showing the operation of the embodiment of Figure 18. Examples of the Invention With reference to Figure 2 components having identical or similar functions to those in Figure 1 described previously are designated by the same reference numerals. An electromechanical actuator of the invention has a stepping motor assembly 11 which comprises a stepping motor 1, and a drive circuit 2, a timing control circuit 3, a serial-to-parallel (S/P) converter 12A and a parallel-to-serial (P/S) converter 12B. These circuits are implemented in an IC chip mounted on a heat conducting, suitably a metal substrate forming part of the motor. The S/P converter 12A converts control signals in the form of serial data into parallel data and holds them. The P/S converter 12B converts signal in the form of parallel data into serial data and holds them. The controller 13 has the same function as the controller 4 in Figure 1. In addition, it converts the control signals of the parallel data into serial data and supplies the serial data through the serial data line 14A to the S/P converter 12A. Control signals in the form of serial data are supplied from the controller 13 to the S/P converter 12A where they are converted into parallel data. The timing control circuit 3 produces drive signals according to this parallel data, and sends them to the drive circuit 2. The drive circuit 2 produces drive currents in accordance with the drive signals, and supplies them to the windings of the respective phases of the stepping motor 1 to drive it. An example of the timing control circuit 3 and the drive circuit 2 is shown in Figure 3. The timing control circuit 3 comprises a microprocessor 31, a ROM 33 storing programs, and a RAM 34 storing various data. They are interconnected via bus 32. The drive circuit 2 comprises a register 34a which receives timing signals from the microprocessor 31 and produces control signal OVDV, ⊘1, ⊘2, ⊘3 and ⊘4. These control signals are supplied through open-collector drivers D0, D1 to D4 to the bases of transistors T01, T1 to T4a whose emitters are grounded. The controller of the transistor T0a is coupled to the base of an additional transistor T0b whose emitter is connected to a over-voltage drive power supply Vp (e.g., 38V). The collector of the transistor T0b is connected to centre taps of stator windings 23A, 23B. Ends of the windings 23A, 23B are connected to the collectors of the transistors T1 to T4. The centre taps of the windings 23A, 23B are also coupled through a diode 40, a resistor 39 to the logic-level power supply Vcc. At the beginning of each cycle for each step, the open-collector driver D0, the transistors T0a and T0b are made conductive by the control signal OVDV, and the over-drive power supply Vp is connected to the stator windings through the transistor T0b. When the transistor T0b is nonconductive, the power supply Vcc of a lower voltage supplies current to the stator windings 23A, 23B. This current produces holding torque when periodical and sequential alternation of the signals ⊘1 to ⊘4 are stopped. When the stepping motor is commanded to complete a certain number of steps, e.g., for a line feed (or carriage return in the case of a printer) through the controller, the signals ⊘1 to ⊘4 are alternated in sequence. The over-drive voltage Vp is applied to the earlier part (after the initial rise) of each cycle for each step. In the latter part of each cycle for each step the lower voltage Vcc only is applied. The voltages are used for rotating the stepping motor 1. Thus the stepping motor 1 is driven as commanded, e.g., to feed printing media by a predetermined amount. After the rotation of the commanded amount, the alternation of the signals ⊘1 of ⊘4 is terminated and the states of the signals ⊘1 to ⊘4 at the time of the termination of the alternation of the signals ⊘1 to ⊘4 are maintained. That is to say two of the signals ⊘1 to ⊘4 that are at a high level at the time the alternation is terminated are kept high and the other two of the signals ⊘1 to ⊘4 that are at the low level at the time the alternation is terminated are kept low. As a result, a holding torque is generated in the stepping motor 1 by the current which flows from the power supply Vcc through the resistor 39 and the diode 40. The holding torque prevents the printing media from being moved too easily by external forces. When the angular movement is completed, parallel data indicating such completion are produced by the timing control circuit 3 and are converted by the P/S converter 12b into serial data and transmitted to the controller 13. Parallel data indicating the temperature within the motor 1 and parallel data indicating disconnection of the wire (or associated connector) are also produced by the timing control circuit 3, and are converted by the P/S converter 12B into serial data and transmitted to the controller 13. As can be seen in Figure 2, the output lines 5 from the drive circuit 2 are disposed within a motor assembly for the motor 1 and need not run external to the housing of the motor assembly 11. The only conductors that must be disposed outside the motor assembly 11 are those for connecting the controller 12 and the S/P and P/S converters 12A and 12B. These conductors include the one 13A for transmission of serial data of control signals and the one 14B for transmission of serial data from the motor assembly 11 to the controller 13. With reference to Figure 4A and Figure 4B the motor assembly 11 comprises an outer frame 21 of a magnetic material such as iron and also serves to provide a mounting flange and a cover for the stepping motor 1. The motor comprises two sections 21A, 21B axially spaced along shaft 28b. Windings 23A, 23B of the sections 21A, 21B are wound in bobbins 24A, 24B, mounted on and fixed to respective metal plates (such as iron plates) 25A, 25B. The ends of the windings are soldered for electrical connection. Each of the metal plates 25A, 25B is wrapped around the winding 23A or 23B on the bobbin 24A or 24B. A radially inner part of the metal plate 25A, 25B is formed into teeth 26 which extend from opposite end parts of the metal plate and which are separated by gap 26G. The teeth 26 from opposite ends have opposite magnetic poles N and S when the winding is excited. The windings of the two sections are offset from each other by 90 electrical degrees, so that the motor can operate in two-phase excitation. A rotor 22 is mounted on the shaft 28b fixed to the outer frame 21. The rotor 22 is formed of a magnet material such as ferrite or a rare earth material. The rotor 22 is magnetized to exhibit N and S poles alternately along its circumference. Magnetic flux created by the excitation of the windings 23A, 23B asses through the metal plate 25, and the teeth 26 to interact with the magnetic poles to produce attracting and repelling forces and hence rotational and holding torques. A circuit pattern (with intervening insulator) is formed on an internal surface of the metal plate 25A and an IC chip 27 is mounted on the metal plate. The S/P converter 12A, the P/S converter 12B, the timing control circuit 3 and the drive circuit 2 are implemented in the IC chip 27. The outputs of the drive circuit 2 are connected to the windings on the pattern of the metal plate 25A. The drive currents are fed through these connections. The conductors for the drive currents are disposed inside the metal plates 25A, 25B except where they pass through the end parts of the metal plates 25A, 25B where they adjoin. Figure 5 shows a actuator system in which a plurality of motor assemblies 11 are connected in parallel with a single controller 13. A serial data line 14 is connected to all the motor assemblies 11-l to 11-N. In the same way as the arrangement of Figure 2, the control signals from the controller 13 are used for driving the stepping motor 1. Select lines 15-l to 15-N are used for conducting select signals, by which the control signals are inputted to the selected one of the motor assemblies 11-l to 11-N. In the above description, the IC chip 27 by which the drive circuit and the like are implemented is mounted in the motor assembly 11. In a modification, a power supply circuit including a DC/DC converter can also be implemented as part of the IC chip. With such an arrangement, a single power supply sufficies for V L and V P . Similarly, a ground line can be shared for E L and E P . In the system of Figure 5, select lines 15-l to 15-N are used for selection of the motor assembly. Alternatively, the motor assemblies 11 and the controller 13 are connected by an address bus through which an address signal is supplied from the controller 13 to the motor assemblies 11. In this case, the motor assemblies 11 should include an address decoder and a switching circuit. In the embodiment described, the motor assembly comprises a stepping motor. The motor assembly can alternatively comprise a DC motor such as a flat-type DC brushless motor. Moreover, the motor can be of any other type. Instead of the motor in which drive currents are supplied to windings, motors which operate on drive voltages can also be incorporated in the motor assembly. In the embodiment described above, a control and drive circuit in the form of an IC chip including an S/P converter, a P/S converter, a drive circuit for producing a drive current or voltage is provided in the motor assembly. The interconnection of a controller and the motor assembly is simplified. Since the conductors for transmitting drive currents or voltages are conveniently covered by metal cover and thereby magnetically shielded leakage of interfering electromagnetic waves can be prevented. Moreover, the circuitry is mounted on a metal plate, whose heat capacity is large, so that effective cooling and heat radiation are ensured. The actuator having a control and drive circuit integral with the motor itself can be used to form a system for accessing or controlling by means of command from a main controller to a plurality of actuators. Description of embodiments of such systems follow: Figure 6 is an overall schematic diagram of the configuration of a first embodiment of such a system. The motor units 110 are connected in series by a serial data line 116 which sends the output from the main controller 106 to the receiver circuit in motor unit 110-1 sends the output from the transmitter in motor unit 110-1 to the receiver in motor unit 110-2, and continues in analogous fashion by sending the output from motor unit 110-(k-1) to the next motor unit 110-k, where 2 k ≧ n. Figure 7 is a block diagram of an example of a motor unit 110. It comprises a motor 101, a drive 102 for sending signals to drive the motor 101, and a control section 120 for sending signals to control the driver 102. Figure 8 is a block diagram of the control section 120. As the diagram shows, the control section 120 has an interface controller 130 which comprises a receiver 131 for receiving serial data from a serial data line 116, a processor 132 for processing the data thus received in a manner to be described later, and a transmitter 133 for sending the data to another actuator if these data are not to be acted on by this actuator. It also has a motor controller 104 which, if the data are to be acted on by this actuator, sends control signals to the motor driver. This embodiment operates as follows. The process performed by the interface controller 130 is set forth in the flowchart in Figure 9. The serial data 140 received by the receiver 131 (step S101) comprise an address field 141 and a data field 142 as shown in Figure 10. The address data (labeled ADD) in the address field are extracted (step S102) and processing by the processor 132 (step S103). The process performed is a decrementation that can be written as ADDM1 = ADD - 1, yielding a result ADDM1 which is compared with fixed data such as 0 (step S104). If the result equals the fixed data, the process branches to step S107: the serial data are recognized as comprising a command for this motor unit and the data (labeled DATA) in the data field 142 are decoded to begin the process of driving the motor. If the decremented value ADDM1 is not equal to the fixed data (such as 0) when compared in step S104, the serial data are recognized as pertaining to another motor unit, and the processed value ADDM1 is set in the address field of the serial data (step S105). The data now consist of the address data 151 (ADDM1) and the data 152 (labeled DATA) in Figure 11. These serial data 150 are for output, and are sent on the serial line by the serial data transmitter 133 (step S106). The next motor unit receives the data thus sent and repeats the same process as above. A major advantage of the above system is that, differing from the serial line system of a prior art, it does not require an address to by hard-wired into the circuit in the motor unit, so the hardware in all the motor units can be identical. The data-processing step in the above arrangement was a decrement process, but an increment process could be used as well and would provide the same effect. Figure 12 is an overall schematic diagram of another embodiment of the actuator control system. As the diagram indicates, the transmitter of the final motor unit 110-n is coupled to a receiver in the main controller 106 enabling bidirectional communication. The configuration of the control section in this embodiment is the same as in Figure 8. The process of bidirectional communication is shown in the flowchart in Figure 13, which corresponds to step S107 in Figure 9. The data field in the serial data includes a command area, and one of the commands can be a READ command. The operations carried out in Figure 13 are the following: when a request to read data comes from the main controller 106, the motor unit, after beginning execution of the command (step S201), decodes the data field (step S202) and determines whether the command is a read command or a motor control command (step S203); if the command is a READ command, the requisite read data (such as status data) are written in the data field 162 of the outgoing serial data 160 and 0 is written in the address field (step S204), then these serial data are sent (step S205). The address field in the read data sent from the motor unit in this way is decremented as it passes through the other intermediate motor units and is received at the receiver of the main controller with the value -m (after passing through m motor units). The main controller can thus determine from which motor unit the message comes. Although the process performed on the address field in the above embodiments was a decrement process, an increment process, a right-shift (divide-by-2) process, or a left-shift (multiply-by-2) process could be used instead. Furthermore, the fixed data need not be 0 but could be the hexadecimal value FF... or any other constant value. Such modifications would not change the operation described in the above embodiments. As explained above, the embodiments of Figures 6 to 14 do not require differing address data to be hard-wired into each actuator, so the entire circuit can be implemented in an integrated-circuit chip, thereby simplifying the production process, reducing costs, and increasing reliability. The above embodiments also enable a large number of actuators to be situated on a single serial data line, thereby reducing the overall number of interconnection lines and offering large advantages in mounting and cost. Furthermore, if the output from the final actuator is returned to the main controller, bidirectional communication with a large number of devices can be easily realized with a small number of bus lines. In a further embodiment of the invention, which is generally identical to that shown in Figures 6 and 7, the control section 220 (corresponding to the control section 120 of Figures 7 and 8) is as shown in Figure 15. As illustrated, it comprises an interface controller 230, and a motor controller 204. The interface controller 230 comprises a processor 232 connected via an input buffer 231 to the serial line 116, an address register 233 for storing an address, a switch 234 for selecting either the data from the input buffer 231 or the output of the processor 232, and an output buffer 234 for output of the data selected by the switch 234 to the serial line 216. This embodiment operates as follows. The overall process performed by the embodiment shown in Figures 15 and 6 is described by the flowchart in Figure 16. When the system in Figure 6 is powered on, first a system power-on reset process is carried out (step S301) in which each actuator is initialized. Next addresses are set in motor units 110-1 through 110-n by signals sent from the main controller 106 (step S302). This step is performed sequentially for motor units 110-1 through 110-n as described later. When all addresses have been set (step S303), command execution begins (step S304). In other words, the main controller 106 accesses a particular motor unit from 110-1 to 110-n by means of an individual address set in step S302. The process performed in the interface controller in the control section in Figure 15 is set forth in the flowchart in Figure 17. When the system is powered on, the control sections are reset by an internal signal, or cleared by input of a Reset signal (step S401). This step initializes all registers and counters in the controller sections and clears all their address registers to the same initial value (0, for example). Next the address-setting mode is entered. The main controller 106 first sends an address-setting command to the first motor unit 110-1 in the series of motor units to which it is coupled. As shown in Figure 10, the serial data 140 received by the motor unit 110-1 comprise an address field 141, in the address area 143 of which is set the value (0) to which the address register was initially cleared, and a data field 142, in the command area 144 of which is set the address-setting command, and in the data area 145 of which is set the address to be assigned to motor unit 110-1 (the address '1' for example). When the motor unit 110-1 receives the above serial data (step S402), it first tests whether the value in the address field 141 of the serial data equals the value (0) in the address register (step S403). If the two values are equal (as they are in this case because both are 0), the serial data are recognized as a command to the first motor unit 110-1. The value in the command area 144 of the data field 142 indicates that the command is an address-setting command, so the value (1) in the data area 145 is latched in the address register 233 (step S404), thus completing the setting of the address of motor unit 110-1. When setting of the address is completed, the processor 232 switches the serial data bus line (step S405). Immediately after the power-on reset (step S401), the switch 234 was closed at A, and the serial data input from the serial line 116 via the input buffer 231 were input to a Serial-Input terminal of the processor 232 so that the processor could decode and execute the command. When the processor 232 receives a READ command directed to it, it causes the switch 234 to close at A by means of a control signal. As a result, READ data output from the terminal S OUT are fed onto the serial line 116. At the completion of address setting, however, the switch 234 is closed at B by a control signal 236 from the processor 232 (step S405). The serial data are then routed from the input buffer 231 via terminal B and the output buffer 235 to the second motor unit 110-2. Next the main controller 106 sends an address-setting command to the motor unit 110-2 which is coupled in the second position in the series. The address field 141 of this command contains the same value (0) as when the address of the first motor unit 110-1 was set. The data area 145 of the data field 142 contains an address (the addres '2' for example) specific to the second motor unit 110-2. The serial data sent from the main controller 106 are input by the first motor unit 110-1, bypassed without alteration via terminal B to the output buffer 235 of the first motor unit 110-1, and input by the second motor unit 110-2 (step S402). The serial data input by the first motor unit 110-1 are also fed via the Serial Input terminal to the processor 232 and compared with the address stored in the address register 233 (step S403), but since the value in the address register 233 is no longer 0 but the specific address ('1') of motor unit 110-1, it is not equal to the value in the address field 141 of the serial data. Accordingly, the serial data are regarded as not constituting a command for the first motor unit 110-1 and are simply output as received with no processing performed (step S406). The value in the address register 233 of the second motor unit 110-2 is still the initial value (0), which matches the value (0) in the address field 141 of the serial data 140, so the serial data 140 are recognized as constituting a command for the second motor unit 110-2 (step S403). The specific address of the second motor unit 110-2 is then set and its serial data bus is switched (steps S404 and S405) in the same way as was done for the first motor unit 110-1. A similar process is repeated until the specific address of the n-th motor unit 110-n has been set in its address register and its bypass circuit has been closed (step S407). When all addresses have been set in this way, the main controller 106 begins sending commands to be executed by the various motor units. These commands are sent in the same serial data format as the address-setting commands, shown in Figure 10. When serial data are received (step S407) by a motor unit, first the value in the address field 141 is compared with the contents of the address register 233 (step S408). If the serial data are thus recognized as a command to this motor unit, the command area 144 in the data field 142 is decoded and the command is executed to drive the motor (step S409). If serial data are sent with the value '2' in the address field, for example, the motor unit 110-2 having the matching value '2' stored in its address register 233 recognizes the match and executes the command. If in step S408 the value of the address field 141 in the serial data does not match the contents of the address register 233, the serial data are regarded as pertaining to another motor unit and are left without taking further action. As explained above, the access system in this embodiment is featured in that it does not require an address to be hard-wired into a circuit in the motor unit. The hardware of all the motor units can therefore be identical. A modification shown in and described with reference to Figures 12 to 14 in connection with the embodiment of Figures 6 to 11 can be made to the above embodiment of Figures 16-18. In this modification, the process of bidirectional communication shown in Figure 13 corresponds to steps S407 through S409 in Figure 17. Among the commands that can be placed in the command area 144 of the serial data is a READ command. In place of '0' being written as described previously in connection with the step S204, the address of the main controller 106, which is set at initialization, is written in the address field 151, then the resulting serial data are sent (step S205). The switch 234 is closed at A in Figure 15 during this process by a control signal 236, the switched back to B after the data have been sent. If the command in the serial data received is determined in step S203 to be a motor control command, the command is executed (step S206) and the process ends. In this way data read from a certain motor unit pass through other intermediate motor units until they can be received by the main controller 106. The value to which the address register 233 is cleared in the above modification was 0, but a value of 1 or any other constant value could be used instead. The embodiments described above with reference to Figures 15 to 18 do not limit the scope of this invention, which can be modified in various ways. Furthermore, it is not always necessary for addresses to be set in all of the actuators; addresses could be set in only those devices which will actually be accessed. The switching circuit can be configured from appropriate logic circuits in various ways. In the embodiments as described above, in order to access a plurality of actuators connected in series to a controller, the control sections in the actuators are provided with an address register than can be externally set. At the initial reset, all these address registers are cleared to the same value, then an address specific to each actuator is set in the address register means of serial data input. The systems of the above embodiments accordingly do not require differing address data to be hard-wired into each actuator, so all the interface controller circuits are identical and can be implemented in an integrated-circuit chip, thereby simplifying the production process, reducing costs, and increasing reliability. The system of the above embodiments also enables as many actuators to be accommodated on a single serial line as the length of the address allow, thereby reducing the overall number of interconnection lines and offering large advantages in mounting and cost. Since any desired addresses can be set, the main controller can easily communicate with all the actuators bidirectionally. In addition, a bypass in the serial data path in each actuator enables the data to be propagated with an extremely short delay, thereby enabling high-speed operation. A further embodiment of this invention will be described next with reference to Figure 18. Figure 18 is a block diagram of an actuator which is in the form of a motor device that is controlled in this embodiment of a control system, i.e., a motor control system of this invention, whose overall system configuration is generally identical to that shown in Figure 6. The motor devices 110 have the following structure. Each motor device 110 comprises a motor 301, a driver 302, and a control section 303. The control section 303 comprises a motor controller 304 and an interface controller 305. These motor devices 110 are characterised in that the interface controller 305 comprises an address register 306, initializing means 307, address-setting means 308, and command-processing/serial-data sending means 309. The address register 306 stores a specific address sent from the main controller 106 for assignment to the particular motor device 110. In other words, a 'soft' address can be set in this address register 306 from the outside. The initializing means 307 are hardware or softward means for resetting or clearing the address register 306 to a fixed value such as 0 when a power-on reset is performed or a Reset signal is received. The address-setting means 308 receive serial data containing the address value to be assigned to the motor device 110 and set this value in the address register 306 in an initial setup process. The command-processing/serial-data-sending means 309 test the value in the address field of serial data received after the initial setup and, if this value equals the address value in the address register of this motor device, regard the received serial data as a command pertaining to this motor device and executes the command, or, if the two values are not equal, regard the data as a command for another motor device and sends the received serial data unaltered to the next motor device. The serial data format is identical to that shown in and described with reference to Figure 10. The operation of this embodiment will now be explained with reference to Figure 19. Figure 19 is a flowchart showing the operation sequence of this embodiment. Step S501 is a reset process performed at power-on or clearing process performed when a Reset signal is received. This process resets all registers and counters in the motor device 110 to their initial values. In the second step S502 all the address registers 306 in the motor devices are cleared to the same value of 0. The above steps are performed by the initializing means 307. Steps S503 through S510 constitute the address-setting mode, in which the main controller 106 (see Figure 6) first sends an address-setting command to the first motor device 110-1 in the series of coupled motor devices. In the address area 142 of the address field 141 of the serial data shown in Figure 10 the main controller 106 sets the value 0 to which the address register was cleared in the reset/clear step, in the command area 144 of the data field 142 it inserts an address-setting command, an in the data area 145 it inserts the address value to be assigned to the motor device 110-1. First the motor device 110-1 receives the serial data (step S503) and tests whether the value in the address field 141 equals the value of 0 in the address register 306. If it dies, the serial data are recognized as a command pertaining to this motor device 110-1 and the process branches to step S505. In this step the contents of the command area 144 of the data field 142 are recognized as an address-setting command, and the value in the data area 145 is latched in the address register 306 to complete the setting of the address of the motor device 110-1. Since the serial data were recognized as a command pertaining to this motor device, the processing stops at this point and data are not set to the next motor device. The processes above are carried out by the address-setting means 308 and the command-processing/serial-data-sending means 309. Next the main controller 105 sends an address-setting command to the second motor device 110-2 in the series of coupled devices. The address field 141 and the command area 144 of the data field 142 of the serial data sent contain the same values as when the address of motor device 110-1 was set--that is, the address value is 0-- while the data are 145 of the data field 142 contains the address value to be assigned to the second motor device 110-2. The serial data sent from the main controller 106 are first input to the first motor device 110-1, which tests the data against the value in its address register 306. Since the value in this address register 306 is no longer 0, it does not equal the value in the address field 141, so these serial data are recognized as not pertaining to the motor device 110-1. The command-processing/serial-data-sending meand 309 of the motor device 110-1 therefore send these serial data onward without alteration to be received by the next motor device 110-2. The value in the address register 306 of motor device 110-2 is still the initial value of 0, matching the value in the address field 141 of the serial data, so the serial data are recognized as a command pertaining to motor device 110-2. The address of motor device 110-2 is then set in the same way as was the address of motor device 110-1. This process is repeated until the address of motor device 110-n has been set, thus completing the setting of all the addresses. When the setting of addresses has been completed, the main controller 106 sends various commands to be executed by the motor devices 110. These commands are sent in serial data having the same format, shown in Figure 10, as the address-setting commands, and are executed by the procedure in steps S507 through S510 by the command-processing/serial-data-sending means 309. Step S507 is for receiving the serial data, which comprise an address field 141 and a data field 142, the data field 142 having a command area 144 and a data area 145. In step S508 the value of the address field 141 is compared with the value of the address register 306 of this motor device. If the two values are equal, the process proceeds from step S508 to step S509, in which the serial data are recognized as a command pertaining to this motor device, the command area 144 of the data field 142 is decoded, and the motor 110-1 is driven. If the value in the address field 141 does not equal the value in the address register 306, these serial data are recognized as pertaining to another motor device and the procedure branches to step S510, in which the command-processing/serial-data-sending means 309 send the serial data onward without alteration. The data thus sent onward are received by the next motor device and the same process is repeated. The system of the above embodiment is characterized in that serial-data-sending means and an address-register-setting means are provided in the motor device, thus eliminating the need for a circuit in which a hard-wired address is set. If therefore has the advantage that the hardware in all the motor devices can be exactly the same. Another advantage is that the fan-out of the serial data is always 1, so adding connections to additional devices does not raise the problem of increasing fan-out. A modification shown in and described with reference to Figure 12 to 14 in connection with the embodiment of Figures 6 to 11 can be made to the above embodiment of Figures 18 and 19. In this modification, the sending terminal of the motor device 110-n is linked to a data-receiving terminal in the main controller 106 to enable communication in both directions. Figure 19 is a flowchart of the main part of the operation of the second embodiment. If, say, a READ command is sent from the main controller 106, the process shown in Figure 13 is performed during the execution of this command in steps S507 through S510. First, in step S201, the command area of the data field in the input serial data is decoded. Step S202 determines whether the command is a READ command or a motor control command (a WRITE command). If it is a READ command, in step S204 the requisite read data are written in the data field 336 of the outgoing serial data and the address of the main controller 106, which is set at initialization, is written in the address field 335. The resulting outgoing serial data are sent in step S205. If the command is a motor control command, it is executed in step S203, then the process ends. The read data sent from the motor device pass through other intermediate motor devices and are received by the main controller 106. The value to which the address register was cleared in the embodiments described above was 0, but a value of 1 or any other constant value could be used instead. In the system of the above embodiment of controlling a plurality of devices connected in series to a controller, the control section of each device comprises an address register, initializing means, address-setting means, and command-processing/serial data-sending means, so it is not necessary for separate address data to be hard-wired into each device. The same circuits can therefore be used for the control sections of all the devices. In particular, all the circuits of devices having identical drivers can be implemented in an integrated-circuit chip. This simplifies the manufacture of the devices, holds down their cost, and increases their reliability. This invention also enables as many actuators as the length of the address allows to be accommodated on a single serial line, thereby reducing the overall number of interconnection lines and offering major advantages in installation and cost. Moreover, since any desired addresses can be set, the main controller can easily communicate with all the actuators bidirectionally.

Claims: An electromechanical actuator comprising an electric motor (1), and timing control and drive circuits (3,2) mounted with the motor (1) in the motor assembly (11), CHARACTERISED IN THAT the actuator further comprises a serial-to-parallel converter in the assembly (11) for converting into parallel data a control signal for commanding the required rotation of the motor (1) ,produced in the form of serial data by a controller (13), the timing control circuit (3) is responsive to the output from the serial-to-parallel converter (12A) for producing a drive signal for controlling the timing of the operation of the motor (1), the drive circuit (2) is responsive to the drive signal for producing a drive current to the motor (1), the timing control circuit (3) indicates the completion of the required rotation of the motor (1) by producing parallel data, and the actuator further comprises a parallel to serial converter (12B) for converting the parallel data from the timing control circuit (3) into serial data and sending the serial data to the controller (13). An actuator according to claim 1 wherein the drive circuit (2) includes switching elements (T) which are turned on and off to control the current to the motor (1). An actuator according to claim 1 or claim 2 wherein the drive signal produced by the timing control circuit (3) is maintained until the completion of the required rotation of the motor (1). An actuator according to any of claims 1 to 3 wherein the controller (13) operates in response to serial data from the parallel-to-serial converter (12B). An actuator according to any of claims 1 to 4 which is one of a plurality of actuators arranged along a common serial line (14), and wherein the timing control and drive circuits (3,2) are adapted to determine the destination of motor control signals passed from the controller (13) along the serial line (14) by having means for receiving destination control signals, means for processing the destination control signals, and means for transmitting the destination control signals to a subsequent actuator along the common serial line (14) if upon processing the destination control signal fails to match data in the processing means or for causing the signals in the processing means to be used for motor control if the destination control signal matches. An actuator according to claim 5 wherein the processing means is adapted to perform a fixed operation on destination control signals until a fixed value is obtained, which is to equal for all actuators along the line (14) to enable a motor control signal associated with the destination control signal to be used for motor control by that actuator along the line (14) at which a match is obtained, the fixed operation optionally being a decrement or increment operation or a left-shift (multiply-by-₂) or right-shift (divide-by-₂) operation. An actuator according to claim 5 wherein the processing means have an address register so that motor control signals for that particular address are used for motor control and address setting means accessible along the common serial line (14) to enable addresses to be set sequentially during an address setting stage. An actuator according to claim 7 wherein the processing means have a by-pass circuit (234) for accessing the next actuator along the line (14A), the by-pass being activated upon completion of address setting and the processing means being arranged to act only on control signals for that address after by-pass activation. An actuator according to claim 8 wherein the processing means has an initialising means and means for executing or inhibiting an address setting command so as to permit sequential address setting. An actuator according to any of the preceding claims 5 to 9 wherein the timing control and drive circuits (3,2) are arranged for transmitting read data along the serial line (14) to a common processor for the actuators. An actuator according to any of the preceding claims wherein the control and drive circuits (3,2) are in the form of an IC chip, the chip optionally including any overdrive power supply means. An actuator according to any of the preceding claims wherein the timing control and drive circuits (3,2) are secured to the motor (1) on a part thereof effective for establishing heat dissipation, preferably on or inside a metal plate surrounding a motor stator winding and preferably forming at least part of a magnetic path for the magnetic flux created by stator windings. An actuator according to any of claims 6 to 12 wherein the fixed value is 0. An actuator according to any of claims 6 to 13, wherein the fixed value is set by hardward or software when actuator power is first switched on.

Inventors: AKUTSU, NAOJI OKI ELECTRIC INDUSTRY CO., LTD., KASAI, TADASHI OKI ELECTRIC INDUSTRY CO., LTD., TANUMA, JIRO OKI ELECTRIC INDUSTRY CO., LTD.
Applicants: OKI ELECTRIC INDUSTRY COMPANY, LIMITED
Application year: 1987
Main classification: H02K11
IPC codes: H02K37, H02P23, H02K11, H02P8