Abstract:
Apparatus, having multiple motor modules, has an MCU module. Each motor module has an electronically controlled motor. The MCU module has an MCU and an interface for connecting to a bus from a CPU. In use the MCU module receives control signals from the CPU and in turn instructs a selected one of the motors to operate.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 0801450.8 filed in Great Britain on Jan. 28, 2008. 
     FIELD OF THE INVENTION 
     The present invention relates to a scheme for controlling a plurality of motors, particularly electronically controlled motors such as brushless DC motors and piezoelectric motors. 
     BACKGROUND OF THE INVENTION 
     Generally, a modern passenger vehicle has many electrically controlled actuators with electric motors. For example, actuators are used in safety mirrors, seats, and vehicle air conditioning systems where they control flaps or barriers used to control or redirect air flow within the vehicle for allowing more or less air to pass over a heat exchanger coil or directing air to certain parts of the vehicle such as windscreen vents or feet vents. The electric motors moving these flaps are generally controlled from a centralized control panel or, when fitted, from a remote control panel. Automate control of the air conditioning system based on sensor feedbacks, etc is also allowed. 
     Previously, these motors were generally PMDC (Permanent magnet direct current) brush motors. This type of motors is easy to control manually, has acceptable life and is relatively cheap. However, they are noisy either audibly, electrically or both. Noise is becoming a problem in the modern passenger vehicle. Audible noise generated by the motors has become very noticeable as passenger compartments are being effectively isolated from road and engine noise. Electrical noise is also undesirable as the modern vehicle has multiple computer systems and electronic devices susceptible to electrical noise. For automated systems controlled by a computer, such as mirror, seat, and temperature controls with memory, the motors are connected to the computer via a computer bus such as a LIN Bus or CAN Bus. Electronically controlled motors are more suited to this kind of system. One drawback to using electronically controlled motors is the cost of the electronics may be more than the cost of the motor being controlled. In an air conditioning system, the temperature changes occur slowly and thus most of the time the motors are idle. The seat and mirror memory systems may be operated only when there is a change of driver. 
     A typical computer controlled system is shown in  FIG. 1 . An on board computer system  10 , which maybe a single computer or a number of computers linked together, is referred to as a CPU. A plurality of motors, M 1 , M 2 , . . . Mn, are connected to the CPU  10  via a LIN bus system  12 . This requires each motor  31  to be fully independent, having its own LIN bus driver  23 , MCU  21 , feedback sensor  33 , power switch  24  and identifier  32 . This is expensive in terms of electronic hardware which is used only occasionally. 
     SUMMARY OF THE INVENTION 
     The present invention aims to reduce the total cost of the electronics for a system having multiple electronically controlled motors by sharing some of the electronic components (circuits) between the motors. This has the added benefit of increasing the reliability of the overall system by reducing the number of possible faults. 
     Accordingly, in one aspect thereof, the present invention provides apparatus comprising: an MCU module having an MCU and an interface for connecting to a primary bus from a CPU; and a plurality of motor modules, each motor module having an electronically controlled motor and an Identifier; wherein the motor modules are electrically connected to the MCU module, and the MCU module receives control signals from the CPU and in turn instructs a selected one of the motor modules to operate. 
     Preferably, the MCU module is connected to the motor modules by a bus. 
     Preferably, the bus carries high voltage AC signals for driving the selected motor. 
     Preferably, the MCU module further comprises a power switch circuit which provides power signals for operating the motors. 
     Preferably, the MCU determines which motor to select in response to a command from the CPU based on information provided by the Identifier. 
     Preferably, the motor module further comprises a feedback sensor for giving information to the MCU about a condition of the motor. 
     Preferably, the electronically controlled motors are piezoelectric motors. 
     Alternatively, the MCU module is connected to the motor modules by low voltage signal wires. 
     Accordingly, in a second aspect thereof, the present invention provides a method of controlling multiple electronically controlled motors, the method comprising the steps of: connecting a MCU to a bus from a CPU; connecting the MCU to the plurality of motors; using the MCU to select which motor to operate and in which direction based on the signals received by the MCU from the CPU. 
     Preferably, the method includes the steps of providing each of the motors as part of a motor module and connecting each motor to the MCU via an Identifier located in the motor module. 
     Preferably, the method includes the steps of providing a power switch circuit in each motor module to drive the respective motor. 
     Preferably, the method includes the steps of providing a power switch circuit in the MCU module and sharing the output from the power switch circuit with the motor modules. 
     According to a third aspect thereof, the present invention provides a method of controlling multiple electronically controlled motors, the method comprising the steps of using a single MCU to interface between the multiple motors and a CPU. 
     Preferably, the method includes the step of providing a single power switch circuit to selectively operate each of the motors and using the MCU to select which motor is to be operated based on instructions from the CPU. 
     Preferably, the method includes the steps of providing feedback sensors associated with each motor and passing signals from the feedback sensor to the MCU to determine when to deselect the selected motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a motor control scheme according to a conventional method; 
         FIG. 2  is a block diagram of a multiple motor system according to first embodiment of the present invention; and 
         FIG. 3  is a block diagram of a multiple motor system according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 2  shows a block diagram of a multiple motor system or assembly in accordance with a first preferred embodiment of the present invention. A bus which we call primary bus  12  is connected to a CPU  10 . The primary bus  12  may be a LIN bus (Local Interconnection Network bus), a CAN bus (Controller Area Network bus) or a bus of another protocol. The primary bus  12  connects the CPU  10  to a MCU module  20  and some other components (not shown in the figure) which are generally known to those skilled in the relevant arts. The MCU module  20  is connected to a plurality of motor modules  30 , designated as M 1 , M 2 , . . . Mn, via another bus  22 . The bus  22  is a low voltage signal bus carrying only low voltage signals for controlling the motor modules  30 . 
     The MCU module  20  has an MCU  21  and a primary bus driver  23 . The primary bus driver  23  enables the MCU  21  to send and receive signals over the primary bus  12 . Each motor modules  30  comprises an electronically controlled motor  31 , a power switch  24 , an Identifier  32  for communication with the MCU  21 , and optionally, a feedback sensor or circuit  33 , such as a position sensor. The bus  22  could be a hard wired bus if the number of motor modules  30  is small, otherwise a dedicated computer bus is preferred. 
     Thus, in this simple embodiment, a single MCU  21  is shared by all of the motor modules  30  of the system or motor assembly, thereby greatly reducing the total cost of the system. Also, only one primary bus driver  23  is required. 
       FIG. 3  illustrates a multiple motor system in accordance with a second embodiment of the present invention. In the embodiment, the MCU module  20  also has a power switch circuit  25 . Thus each motor modules  30  includes only the motor  31 , the Identifier  32  and the optional feedback sensor  33 . In this embodiment, the local bus  22  carries both low voltage control signals as well as power signal. For a stepper motor, a brushless DC motor or a piezoelectric motor, etc., these power lines would carry high voltage pulses to operate the motors. 
     In this second embodiment, the motor modules  30  share a common MCU  21 , the power driver circuit  25  and the primary bus driver  23 , thus further reducing the complexity and total cost of the system or apparatus. 
     In accordance with a preferred embodiment of the present invention, the electronically controlled motors in above embodiments are piezoelectric motors. In this scenario, the MCU module has a piezoelectric driver circuit and each motor module simply connects the motor to the driver signals sent out by the MCU module when that motor is selected to be activated. Selection is achieved by way of the Identifier. The driver signals are high voltage AC signals but the current level is relatively low compared to other types of DC motors. However, the arrangement can be used for other types of electronically controlled motors especially if the motors are physically located close by so that the bus  22  is short. 
     Thus it can be seen that the preferred embodiments of this invention reduce the complexity and cost of the multiple motor system by sharing a number of electronic components between motors. 
     In the description and claims of the present application, each of the verbs “comprise”, “include” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item but not to exclude the presence of additional items. 
     Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow. 
     For example, while the invention has been described with reference to an air conditioning system for a passenger vehicle, it could be applied to other multiple motor systems found within a vehicle, such as the seat and mirror control and memory systems. Indeed, the invention could be applied to multi-motor systems of non-automotive applications. 
     Definitions of some of the abbreviations used in this description are: 
     CPU—Central Processing Unit 
     MCU—Micro Controller Unit 
     LIN bus—Local Interconnection Network 
     CAN bus—Controller Area Network 
     The term CPU or Central Processing Unit, can be used to refer to the processing chip within a computer or it may refer to the unit doing the data or signal processing and includes a computer, a series of computers and a central data processing processor. The computer system of the modern vehicle may have a number of computers working together in a distributed computer network and any of these computers, or all of the computers collectively may be referred to as the CPU. 
     LIN bus and CAN bus are two well known examples of primary bus protocols used in vehicle computer systems.