FR2644306A1 - System for controlling a DC electric motor, advantageously for motor vehicle - Google Patents

Abstract

The invention relates to a system for controlling an electric motor, especially a DC motor. The system is of the type comprising a DC current source such as a battery 18, a device 17 for varying the current of the motor and means 10 for controlling the variator device. It is characterised in that it comprises a data processing unit 1, such as a computer device programmed to determine the current of the motor according to programmable criteria, and to accomplish additional functions relating to the management and safety of the system. The invention can be used for the motors of motor vehicles.

Description

 The subject of the invention is a system for controlling a direct current electric motor, advantageously for a motor vehicle, of the type comprising a direct current source such as a battery, a device for varying the current of the motor and means for drive device control.

 Known systems of this type have the drawback of being limited, due to their very design, to the sole problem of the strict operation of the motor under the effect of the current variation device.

 The object of the present invention is to propose a system of the type described above, which provides an improvement in the control of the motor itself, and is able to perform additional functions relating to this motor in its environment determining the field of application of it. The system according to the invention is thus designed to ensure engine safety by periodically monitoring the essential elements and parameters of the engine and of the system and allows optimal management in the respective application domain and optimization of its performance due to the fact that it constitutes an advanced so-called "human-machine relationship" tool.

 To achieve this object, the system according to the invention is characterized in that it comprises a data processing unit such as a computer device, in particular a microcomputer, programmed to determine the motor current according to programmable criteria, and for perform additional functions related to system management and security.

 According to an advantageous characteristic of the invention, the system has a modular structure comprising an interface module interposed between the data processing unit and a power module comprising said motor and suitable for conditioning the external control signals and parameters to be monitored, to transmit these signals to the data processing module so that they are processed in this module and to transmit to the power module the engine control signals, which result from this processing.

The invention will be better understood, and other objects, characteristics, details and advantages thereof will appear more clearly during the explanatory description which follows, made with reference to the appended schematic drawings given solely by way of example illustrating a embodiment of the invention and in which
- Figure 1 is a block diagram of a system according to the present invention; and
- Figures 2 and 3 show part of the structure of the interface module indicated in II in Figure 1.

 As is clear from Figure 1, the control system of a direct current electric motor for example for driving a motor vehicle, has a modular structure. The system according to the invention essentially comprises a data processing module 1 such as a microcomputer programmed to be able to manage all the functions to be performed by the system, a power module 2 which comprises the electric motor, as well as a module interface 3 interposed between the data processing module 1 and the power module 2.

 The interface module is connected to the data processing module 1 by a bidirectional data bus 4 which makes it possible to transmit to the module 1 the data to be processed and to receive from it the data constituting the results of the treatments performed. The interface module transmits to the power module 2 the various control signals of the motor and of the actuation relays of the contactors used in the system, by connections indicated in 5 and 6.

The interface module 3 is associated with a control device 8 comprising external control members.

The device 8 advantageously comprises two types of control members, those which are actuated by the operator of the motor vehicle and those which are integrated into the system and the vehicle and intended to ensure correct operation and safety of the assembly.

The operator actuable control elements essentially comprise an accelerator pedal and control elements for the direction of the engine, that is to say forward and reverse as well as any other contactor which could be advantageous for maneuvering the vehicle. As a safety device, provision could be made for microswitches for hand brakes, seats and any other electrical contact which may appear necessary or advantageous for ensuring the safety of the engine and of the system and, more generally, of the vehicle. .

 More specifically, the interface module 3 comprises a generator 10 of the motor current control signals, which have a constant frequency of for example 20 Khz and are formed by pulses modulated in width. These are therefore signals whose duty cycle varies depending on the position of the accelerator pedal. The generator is connected to bus 4.

The module 3 also comprises an arrangement 11 of control circuits for the relays, also connected to the bus 4, a circuit arrangement 12 also connected to the bus 4 and forming an interface for the processing module for monitoring the system by periodic interrogation. parameters considered essential of the system, as will be explained below, and an arrangement of circuits 13 for shaping the signals coming from the control device 8 with a view to their transfer to the processing module 1 via a connection indicated schematically in 14.

 The power module 2 comprises the direct current electric motor in the example shown of the type switchable between the operating modes with separate excitation and in series. The armature of the motor and its inductor windings are represented respectively at 15 and 16. A switching element produced in the form of a power transistor 17 advantageously with field effect and in MOS technology is mounted in the current supply circuit of the engine. Current is supplied by an electric power source such as a battery indicated at 18. The transistor control electrode is connected to the generator 10 of the interface module 3 by the conductor 5. The signal at the duty cycle modulated in from module 3 determines the speed of rotation of the motor while its direction of travel, forward or reverse, is determined by the position of the contacts all designated by the reference 19. The reference 20 indicates a line contact. The power module further includes the relays indicated at 22 which are intended for actuating the various electrical contacts such as the forward and reverse contacts, seats and if necessary, control of direction of travel at low speed. The excitation circuits for these relays are located in the interface module.

 The data processing unit 1 which is designed around a microcontroller, for example of the INTEL - 8051 family, has the role of managing all the functions to be performed by the system. The structure of the module is based on the principle of a standard computer whose application is defined on the one hand by the resident program and on the other hand at the level of the interface module 3. The processing module 1 can be associated a device allowing the operator to dialogue with this module 1. It is therefore a so-called "man-machine relation" tool which could be produced in the form of a terminal 24 formed for example by a standard serial link of the "RS 232" type comprising a keyboard-screen assembly or a microcomputer of the "PC" or other type, or in the form of a display module 25 for example with 16 characters and provided with two push buttons for the given operations . In general, these two modes of communication make it possible to consult system data, program / edit its operating parameters, edit messages for the operator or request a test. / diagnosis of parts or elements of the system. The device of the terminal type also offers the possibility of controlling the system according to the invention by a computer system for particular applications.

 The system can also be equipped with an "integrated access" management device developed around a programmable electronic key, indicated at 26. This electronic key device comprises a non-volatile memory, for example of the EEPROM type which may contain information allowing several types of management.

You can establish a system / key pair, it can be a universal key with the system code. An open group can thus be defined by making a key give access to a group of systems which recognize it, and a credit for time of use could be allocated to the key. We could also form a closed group by making a key give access to a system of any group which recognizes it, a credit for time of use can be allocated to the key. It should be noted that these latter types of management are particularly usable for management of the vehicle rental type. Of course, any other function could be performed by writing appropriate data to the memory of the key.

 Referring to FIGS. 2 and 3, the structure of the interface module 3 will be described below in more detail.

 In these figures, a double line represents the data bus 4 by which the data processing module 1 and the interface module can communicate. In the example shown, this bus is multiplexed so that it can serve as a data bus and an address bus. The blocks represent integrated circuits which are commercially available. These integrated circuits will be defined by their commercial name. Therefore, only the connection of the input or output terminals will be described hereinafter as much as is necessary for understanding the invention, the connections of the other terminals emerging from the figures and being moreover known.

 The generator 10 of the control signals of the power switch transistor 17 of the power module 2 according to FIG. 1 will first be presented.

This generator is recognizable in FIG. 2 by the dashed line which surrounds it.

The generator 10 comprises an arrangement generating a 20 Khz signal, which comprises, arranged in series, an oscillator circuit 29 generating a signal of 10.24 MHz, a divider by two 30 of the frequency of this signal, a set of two meter boxes 31, 32, with 4 bits each formed by an integrated circuit marketed under the name HC 163, which are mounted as an 8-bit meter and a NAND gate 33 mounted as an inverter. The generator 10 further comprises an 8-bit counter formed by the arrangement shown of two integrated circuits HC 193. The CPD input of the circuit 34 is connected to the terminal Q of the divider by two 30 and thus receives a signal of 5120 KHz. The inputs 11 of the two counter circuits 34 and 35 are connected to the output of the NAND gate 33 and thus receive a signal of 20
KHz. Terminals 13 and 4 respectively designated TCD and
CPDs are interconnected. The terminals 15, 1, 10 and 9 of the two integrated circuits 34, 35 are connected to the 8 output terminals of a latching memory circuit 36 of the type
HC 374 whose input terminals are connected to the data bus 4. The output 13 of the counter element 35 is connected to the erasure input CL of a flip-flop of type D 37 whose clock input is connected to the output of the NAND gate 33. The output Q of the flip-flop is connected via an interface circuit schematically indicated by block 38 to the control electrode of the power transistor 17 of the power module 2, via connector 5.

 Referring to FIG. 3, it can be seen that the arrangement 11 of the excitation circuits of the relays 22 of the power module 2 essentially comprises a latching memory 39, the 8 inputs of which are connected to the 4 to 8 bit data bus. This integrated circuit is also of the HC 374 type. Six of these output terminals are connected to a set 40 of 8 reversing buffers contained in a case of the HC 240 type. The 6 corresponding outputs of this case are each connected via a resistor 41 at the base of a transistor 42 mounted in one of the excitation circuits of the relays 22 of the power module 2. To this end the collector of each of these transistors is connected by one of the connections indicated generally at 6 in Figure 1 to the coil of the corresponding relay.

 Returning to FIG. 2, it can be seen that the monitoring interface device 12, also delimited in the figure by a dashed line essentially comprises a number of buffers for bus access buffers, indicated at 43a, b, c, of the HC 244 type. These buffers each include 8 outputs which are in the state of high impedance when the buffers are not energized and transfer to their output terminals the state present at their 8 input terminals in the event of excitation of the buffer. The inputs of these buffers are connected in groups of six to level 44 adaptation buffers which have the function of presenting at their output terminals a level compatible with that of the bus access buffers 43. The inputs of these buffers adapter 44 receive the parameters to be monitored.

Thus the adaptation buffer 44 shown is arranged to allow reading of the states of the transistors 42 located in the excitation circuits of the relays 22 (FIG. 3). To this end, the collector of each transistor 42 located in the excitation circuit of a relay 22 is connected by means of a mounting of a resistor in series 45 and a resistor connected to ground 46 to one of the 6 adapter buffer inputs 44.

In FIG. 3, 48 and 49 show two connections of two transistors 42 connected to two inputs of the adapter buffer 44. It is obvious that the number of bus access buffers 43 and the number of adapter buffers 44 will be chosen by depending on the number of parameters to monitor.

 In FIG. 2, it is further recognized the presence of an address decoder 50 of the HC 138 type which is connected by a locking buffer 51 of the HC 374 type to the bus 4. The buffers 50 and 51 present in the example 5 inputs are shown, of which inputs 1, 2 and 3 of the address decoder 50 are effective inputs while inputs 4 and 6 are validation inputs.

The inputs 5 and 11 of the buffers 50 and 51 respectively receive control signals from the data processing module 1. The three outputs 13, 14 and 15 of the decoder 50 produce signals called respectively CN, CT, PW for controlling the locking pad 36 of the generator 10, locking pad 39 of the device for controlling the relay excitation transistors (FIG. 3) and the bus access buffers 43a, b, c. In order to excite these buffers, each of them is associated with an OR gate with two inputs of the HC 32 type. The gate associated with the locking buffer 36, indicated at 53 receives the signal PW at one of these inputs produced by the decoder 50 while its other input receives the write command signal called WR produced by the processing module 1. The output of the gate 53 is connected to the terminal 11 for controlling the buffer. To the locking buffer 39 gate 54 is associated, the two inputs of which respectively receive the signal WR from the decoder 50 and the signal
Processing module write RR. The output of the door is connected to terminal 11 of the buffer. The gate 55 which receives at its inputs the signal CN from the decoder and the read signal called RD from the processing module is connected by its output to the two terminals 11, 19 of the bus access buffer 43a, while the buffers 43b and 43c are controlled by gates 56 and 57 respectively. The gate 56 receives at these two inputs the signal PW from the decoder 50 and the signal RD from the processing module. Gate 57 on its side receives the CT signals from the decoder and
RD of the processing module.

 The operation of the system will be described below, which will also reveal the particular aspects of the program which the processing module 1 executes.

 It appears from the description of the structure of the system that the processing module 1 performs a certain number of functions to ensure engine control and the safety of the assembly it equips.

The engine control signals are established as follows: when the operator actuates the accelerator pedal of the control device 8, an analog electrical signal, which corresponds to the position of the pedal, is sent to the interface module 3 and transmitted after a formatting operation to the data processing module 1 to be processed there digitally. After its conversion to digital, the signal is subjected to digital filtering which has the purpose of imposing in a predetermined and programmed manner a response time of the engine revving with respect to the operator's command. This limits the current draw of the motor in the event of a sudden start.The transfer function of the digital filter can be described by the following digital function
(n) = lx (n) - Yr, ~ 1 Y (n ~ l)
Ko where Y and Y (nl) represent the transfer values to
n instants n and nl, X represents the numerical value of the position of the accelerator pedal and KO determines the time constant of the filter. The numerical value Y (n) thus obtained can be treated or not by a compression function which can be of the logarithmic type to obtain a smoother control at low speeds.

 The digital signal is then transmitted to the 4 to 8 bit bus which conveys this signal to the interface module 3. However, the instruction for transfer to the bus requires prior validation. Indeed, if during the previous interrogation of the various operating parameters and of the components of the engine and of the system, that the processing module performs within the framework of the monitoring function, this module has noted an abnormality or a fault, or if the conditions necessary for operation are not all met, the transfer will be blocked. The numerical value of the position of the accelerator pedal after its transfer to the bus 4 is stored in the locking buffer 36 following activation of the latter under the appropriate control of the address decoder 50, this is i.e. when the states O have been applied to the two inputs of gate 53. This means that the transfer of the value in digital code from the accelerator pedal will only take place after an appropriate addressing of the generator to the 'predetermined instant during the work cycle determined by the program of the processing module 1. From this value in digital code, the 8-bit counter circuit formed by the counter blockers 34, 35 produces an output signal which will be applied to flip-flop 37 which is arranged such that the output signal from this flip-flop has a length which is determined by the value of the digital signal stored in the locking buffer 37. , the fact that each counter boot 34, 35 receives at its input 11 every 50 milliseconds, a pulse coming from the output of the NAND gate 33 and that the assembly formed by these two booters receives at its input CPD the 5.12 MHz signal present at the output of the divider 30, there is a splitting of the signal period of 20 Kz into 256 elements. This counter assembly generates at its output 13 a signal which is equal to the product of an element of the signal period of 20 Kz and the binary code present at the output of the locking buffer 37. The flip-flop 38 is arranged so that the state at its clock input connected to the output of the NAND gate 33 is transferred to its output Q when the signal RST is at state 1 and the output 13 of the counter assembly goes from state O to 1. The output state of the door being at O, the output Q of the flip-flop therefore goes to state 0. This output signal is then applied, via the interface stage 39 to the control electrode of the power transistor 17 of the power module 2. This control signal has a duty cycle which corresponds to the analog value determined by the position of the accelerator pedal. Thus, to modulate the energy supplied to the electric motor, the voltage of the battery 10 is cut by the transistor 17 which is controlled by the square signal from the generator 10 and whose duty cycle is a function of the maneuvers performed by the operator . The duty cycle can take the values from O to 255, which gives a resolution of 1 in 256.

 During the working cycle interval of the data processing module I which is determined by the state O of the write signal WR coming from this module and the state O of the output signal CT of the address decoder 50, the six excitation transistors 42 of the relays 22 of the power module are controlled by the module 1, by means of the locking buffer 39 and the reversing assembly 40. It can thus be seen that all of the control signals of the motor have been previously processed by module 1 which is, on the other hand, programmed to block these signals following the detection of an abnormality or a fault.

 To be able to inhibit the signals and thus effectively protect the motor, the processing module 1 is programmed to periodically collect information on the state of the parameters and elements of the system, by periodic interrogation. As indicated above in the description of FIG. 3, each of these parameters determines the state of an input of an adapter buffer 44. The states of these buffers are transferred to the inputs of the access buffers to the bus 43. For example, the six inputs of the buffer 43a which are connected to the outputs of the adapter buffer 44 shown reflects the state of the six transistors 42 and thus the state of the six relays 22. The states at the inputs of the three buffers 44a to 44c are successively transferred to bus 4 following an addressing. appropriate done by module 1 and according to the signals at the inputs of their OR control gates 55, 56 and 57. Thus each buffer 43a-c puts at the determined interval an 8-bit information word on the bus. The processing module recognizes the state of the various parameters by the position of the information bit in the word which has been transmitted to it through the bus 4. The processing module analyzes the data thus received to determine the validation or blocking of the signals to be transferred to the interface module 3 through the data bus 4.

 The data processing module 1 is programmed to allow a dialogue with the operator. To this end, the display module 25 interfaces with the operator. It serves as an output device for the processing module. With a capacity of 16 characters it will be used to display alarm signaling information, fault signaling, system-specific data, results of interrogations or tests, state of charge, speed and the motor current, information relating to the management of the electronic key, service messages, etc. The two aforementioned push buttons are used to dialogue with the processing module from an established protocol.

The operator or user of the system can then consult the various data or information accessible and, in particular, consult and / or modify the parameters of the system. Regarding the program of the processing module 1, it should be noted that it has a so-called "real-time" architecture. All the functions are performed in real time except for example a test of the physical devices which is launched as the main task and which monopolizes the processing for its execution.

 Among the multiple functions that the program performs, we could indicate the functions of motor control, security, maintenance, self-diagnosis, management by electronic key, display of information, programming of parameters management of the motor configuration by appropriate coupling of the inductors.

 When the engine starts, the processing module launches a configuration test which makes it possible to know what the hardware configuration allows for operation. A maintenance task which operates continuously checks on the one hand the state of the organs and elements of the systems and on the other hand, the relative consistency between the different tasks executed by the processing module. In the event of a defect found, a defense is executed to ensure the safety of the unit and of the operator. A message indicating the nature of the problem is transmitted to the display module.

 The system according to the invention makes it possible to modify and / or consult a large number of parameters of the system, relating to the operation of the engine, the parameter and the management using the electronic key.

 The system as described, due to its modular structure and the digital processing of data, is easily adaptable to various applications and different operating conditions. Thus, additional power transistors could be provided, in parallel with transistor 17, and of course increase the number of contacts, for example safety and control contacts and the number of contact actuation relays.

Claims (11)

 1. Control system for an electric motor, in particular direct current, advantageously for a motor vehicle, of the type comprising a direct current source such as a battery, a device for varying the current of the motor and means for controlling the variator device. , characterized in that it comprises a data processing unit (1), such as a computer device programmed to determine the motor current according to programmable criteria, and to perform additional functions relating to the management and security of the system.  2. System according to claim 1, characterized in that it has a modular structure comprising an interface module interposed between the data processing unit (1) and a power module (2) comprising said motor (15, 16), and suitable for conditioning the external control signals and parameters to be monitored, for transmitting these signals to the data processing module so that they are processed in this module and for transmitting the signals from the power module (2) motor control, which result from this processing.  3. System according to one of claims 1 or 2, characterized in that the power module (2) comprises the electric motor and the members (17, 19) necessary for its control as well as the actuating relays (22) of these organs.  4. System according to one of the preceding claims, characterized in that the device for varying the supply current of the motor comprises switch means (17) mounted in the supply current circuit, such as at least one transistor power (17), which is controlled by an impulse signal having a constant frequency and having a duty cycle which varies according to the control of an external engine control member, such as an accelerator pedal.  5. System according to claim 4, characterized in that the interface module (3) comprises a device generating (10) the impulse signal, an arrangement (11) of excitation circuits of the relays (22) above, an arrangement (12) of interface circuits for monitoring engine and system parameters and an arrangement (13) of circuits for shaping the external control signals to be transmitted to the processing module (1), the generating devices (10 ) and the arrangements of excitation circuits (11) and interface circuits (12) being capable of being connected to a data bus connecting the interface module (3) to the data processing module (1) .  6. The system as claimed in claim 5, characterized in that the data processing module (1) is programmed to carry out successive work cycles each comprising the sequence of the above-mentioned functions for determining the motor current and the aforementioned management functions and security, the generator device (10) and the arrangements of excitation circuits (11) and interface (12) above being successively connected to the data bus during each cycle.  7. System according to one of claims 4 to 6, characterized in that the device generating (10) the impulse signal for controlling the motor comprises a circuit generating (29-33) rectangular pulses whose width is proportional to the value in digital code of the signal from the external engine control unit such as the accelerator pedal.  8. System according to one of claims 4 to 7, characterized in that the arrangement of the excitation circuits (il) of the relays (22) is connected to the data bus (4) by a locking buffer (39) which is capable of being activated by appropriate addressing on the part of the data processing module (1), and the state of the output terminals of which control switching elements (42) such as transistors mounted in the excitation circuits relays (22).  9. System according to one of claims 4 to 8, characterized in that the arrangement of the above-mentioned interface circuits (12) comprises level adapter buffers (44) which receive signals representative of the signals at their input terminals. parameters to be monitored and the output terminals of which are connected to the bus access buffer inputs (43) capable of being activated by the appropriate addressing on the part of the data processing module (1).  10. System according to one of the preceding claims, characterized in that devices allowing the user to interact with the data processing module (1) are associated with it, such as a terminal (24) of the screen keyboard type, a microcomputer from an external network or a display module 25, to allow functions such as consultation of the system data, programming / editing of the operating parameters thereof editing messages for the user, requesting a test / diagnostic function of parts or elements of the system or the like.  11. System according to one of the preceding claims, characterized in that a management device such as a memory electronic key device is associated with the data processing module (1) in particular to make the use of the system dependent on prior authorization from the data processing module (1).