Electric power steering device and control method

Abstract

To establish control by which steering feeling by an operator is prevented from being affected in a configuration of an electric power steering device using asynchronous communication.SOLUTION: An electric power steering device includes: a torque sensor configured to detect a torque value around a steering shaft of a mechanism part; a receiver circuit configured to receive a communication message including the detected torque value by using asynchronous communication; and a memory in which data of the received communication message associated with a time stamp indicating a time related to the reception is transferred and stored; derivation means configured to derive the torque value at predetermined timing by performing interpolation with the use of two communication messages associated with time stamps that have values before and after the predetermined timing set based on a time of derivation processing for deriving torque values used in assist force calculation processing periodically executed; and processing means configured to perform the assist force calculation processing for the mechanism part with the use of the derived torque values.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an electric power steering device and a control method. [Background technology]

[0002] In recent years, in various devices, a configuration in which a sensor detects a state and performs control based on the detection signal has become widespread. One example of such a device is an electric power steering device that performs assist control related to steering of a vehicle. In an electric power steering device (EPS: Electric Power Steering), a torque around a steering shaft is detected, and assist control of a steering operation is performed using a motor according to the torque value. At this time, a certain deviation occurs between the timing of transmission and reception of a detection signal from a torque sensor and the timing of derivation processing of a control value related to steering. In particular, when asynchronous communication is used for transmitting and receiving a signal, due to its characteristics, a fluctuation occurs in the acquisition timing of the signal. If the steering force is derived without considering the fluctuation, it may affect the steering feeling of a user.

[0003] For example, Patent Document 1 discloses a configuration for motor control in which the time difference between the reception timing of serial signal communication and the start of a current control cycle is monitored to synchronize the control cycle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4491083 Summary of the Invention [Problem to be solved by the invention]

[0005] In devices such as EPS, circuits may be configured with asynchronous communication for cost reasons. Even in such a configuration, there is a need for control that takes into account discrepancies (delays) in the timing of signal acquisition and minimizes the impact on the steering feel felt by the operator.

[0006] In view of the above problems, an object of the present invention is to realize control in an electric power steering device configuration using asynchronous communication that suppresses the effect on the steering feel by an operator. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following configuration. That is, the present invention is an electric power steering device, A torque sensor that detects a torque value around a steering shaft of the mechanism; a receiving circuit that receives a communication message including a torque value detected by the torque sensor using asynchronous communication; a memory for storing data in which a communication message received by the receiving circuit is associated with a timestamp indicating the time of reception of the message; a derivation means for deriving a torque value at a predetermined timing by performing interpolation using two communication messages associated with time stamps having values ​​before and after a predetermined timing set based on a time of a derivation process for deriving a torque value used in a periodically executed assist force calculation process, among the communication messages stored in the memory; and a processing means for performing a calculation process of the assist force for the mechanical portion by using the torque value derived by the derivation means; has.

[0008] Another aspect of the present invention has the following configuration. A torque sensor that detects a torque value around a steering shaft of the mechanism; a receiving circuit that receives a communication message including a torque value detected by the torque sensor using asynchronous communication; a memory for storing data in which a communication message received by the receiving circuit is associated with a timestamp indicating the time of reception of the message; A control method for an electric power steering device, comprising: a derivation step of deriving a torque value at a predetermined timing by performing interpolation using two communication messages associated with time stamps having values ​​before and after a predetermined timing set based on a time of a derivation process for deriving a torque value used in a periodically executed assist force calculation process, among the communication messages stored in the memory; a processing step of performing a calculation process of the assist force for the mechanism unit using the torque value derived in the derivation step; has. Effect of the Invention

[0009] According to the present invention, in an electric power steering device configuration using asynchronous communication, it is possible to realize control that suppresses the effect on the steering feel by the operator. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an example of the configuration of a processing unit and its surroundings of an electric power steering device according to an embodiment of the present invention; [Diagram 2] FIG. 4 is a diagram for explaining an example of signals in asynchronous communication according to an embodiment of the present invention. [Diagram 3] 4 is a timing chart for explaining the timing of signal processing according to an embodiment of the present invention. [Figure 4] FIG. 4 is a graph illustrating a control result according to an embodiment of the present invention. [Diagram 5] FIG. 4 is a graph illustrating a control result according to an embodiment of the present invention. [Figure 6] FIG. 4 is a graph illustrating a control result according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment for carrying out the present invention will be described with reference to the drawings. Note that the embodiment described below is one embodiment for explaining the present invention, and is not intended to be interpreted as limiting the present invention, and all configurations described in each embodiment are not necessarily essential configurations for solving the problems of the present invention. In addition, in each drawing, the same components are given the same reference numbers to indicate their correspondence.

[0012] <First embodiment> A first embodiment of the present invention will be described below. The present invention is widely applicable to devices related to signal control using asynchronous communication, but in this embodiment, an electric power steering device (EPS: Electric Power Steering) mounted on a vehicle will be described as an example. Also, the standard of asynchronous communication between circuits or devices is not particularly limited, but here, a configuration using SENT (Single Edge Nibble Transmission) communication, which is a well-known asynchronous communication standard, will be described as an example.

[0013] [Configuration overview] FIG. 1 is a schematic diagram showing an example of the configuration of an EPS 100 according to this embodiment. The EPS 100 according to this embodiment is configured to include a steering shaft rotation mechanism 101, a torque sensor 102, and an ECU (Electronic Control Unit) 200. The EPS 100 is provided with a motor 103 for providing an assist force related to steering according to a control signal from the ECU 200. The EPS 100 may also be provided with various other components, but these will not be described here and the description will focus on the configuration according to this embodiment. In FIG. 1, the EPS 100 is mounted on a vehicle (not shown) and realizes the running of the vehicle in cooperation with an ECU and other mechanisms separately provided in the vehicle.

[0014] In FIG. 1, the torque sensor 102 is duplicated by detection circuits 102a and 102b, each of which detects a torque value around a steering shaft (more specifically, a torsion bar). The torque sensor 102 is not limited to being duplicated, and may have a further multiplexed configuration. In this case, the detection results of some of the detection circuits may be configured as a backup to be used in the event of a malfunction. In this embodiment, the torque sensor 102 may be a TOS (Torque Only Sensor) or a TAS (Torque Angle Sensor). The torque sensor 102 transmits a detected signal to the ECU 200 by SENT communication, which is asynchronous communication. That is, in this embodiment, the detection circuits 102a and 102b each also operate as a transmission circuit compatible with SENT communication.

[0015] The ECU 200 includes a receiving circuit 201, a register 202, a timer 203, a processing unit 204, and a memory 205. The receiving circuit 201 receives a signal (communication message) transmitted from the torque sensor 102 by SENT communication. The receiving circuit 201 stores the received communication message in the register 202 in association with a timestamp. Time information indicated as the timestamp is obtained by referring to the timer 203. The register 202 temporarily stores the communication message and the timestamp received by the receiving circuit 201, and transfers them to the memory 205 at a predetermined timing. The timing of storing various data in the register 202 and the memory 205 will be described later with reference to FIG. 3.

[0016] The register 202 is a primary storage area, and in this embodiment, is configured to be able to store at least a plurality of communication messages received in SENT communication. The timer 203 measures time and provides time information upon request. The processing unit 204 provides various functions, for example, by reading and executing programs and data stored in the memory 205. In this embodiment, the processing unit 204 is configured to at least realize control processing, which will be described later. The memory 205 may include a cache memory, a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. In this embodiment, the memory 205 is configured to be able to store at least a plurality of communication messages of SENT communication, which will be described later, as a data storage area.

[0017] 1 is duplicated, and the processing unit 204 and the like may be configured to execute the same processing for both communication signals. Here, the description will be given focusing on one of the signals.

[0018] [Communication configuration] In this embodiment, SENT communication, which is asynchronous communication, is performed between the torque sensor 102 and the ECU 200. FIG. 2 is a schematic diagram for explaining communication messages and communication times of the SENT communication in this embodiment. Since the SENT communication is a known standard, detailed explanation is omitted and only an outline is shown. In the SENT communication, one communication message starts with a Sync pulse and includes a 32-bit status nibble (not shown), a Data nibble, a CRC, and an optional Pause pulse. Normally, the same calculation period is set for the transmitting side and the receiving side of the asynchronous communication, but a clock error may occur between them. In this case, an error of about 10% may occur. More specifically, the following communication time may be required for transmitting and receiving one communication message.

[0019] Minimum communication time: 439 [μs] (hereinafter referred to as "Smin") Standard communication time: 484[μs] Maximum communication time: 539 [μs] (hereinafter referred to as "Smax")

[0020] When processing is performed using a received communication message, input processing of the communication message used in the processing, signal processing of the input communication message, and assist force calculation processing using the signal processed are performed according to a predetermined cycle. On the other hand, in asynchronous communication such as SENT communication, since synchronization cannot be achieved between devices that transmit and receive, fluctuations in communication time may occur for each cycle within the range described above. In signal processing, the communication message stored in the memory at that time is the target, but if there is a difference in communication time as described above, depending on the timing, variations may occur in the communication message to be processed. Therefore, fluctuations also occur when deriving the assist force of the steering torque based on the communication message, and the influence of the fluctuations becomes large especially when the fluctuation speed of the steering torque is high. In other words, although the torque sensor detects the torque value at a certain interval, it becomes difficult to stably obtain the torque value detected by the torque sensor at the certain interval due to fluctuations in communication time. In other words, the detection timing of the torque value to be used in the derivation process of the assist force may vary depending on the timing of the derivation process of the assist force. As a result, when the derived assist force is fed back to the mechanism 101 of the EPS 100 for assist control, this may affect the steering feeling of the operator.

[0021] A more specific description will be given. For example, assume that the input process is performed at a cycle of 500 μs and the signal process is performed at a cycle of 1 ms. When the receiving circuit 201 completes reception of one communication message, the message is temporarily stored in the register 202. At this time, time information at the time when reception of the communication message started is specified. The information stored in the register 202 is transferred to the memory 205 by the input process.

[0022] The latest communication message stored in memory 205 is associated with a timestamp that is at least 439 μs old and at most 1078 (=539×2) μs old when the timing of starting input processing is used as a reference. Also, the immediately previous communication message stored in memory 205 is associated with a timestamp that is at least 878 (=439×2) μs old on the receiving side and at most 1617 (=539×3) μs old when the timing of starting input processing is used as a reference.

[0023] In this embodiment, signals for performing accurate assist control are specified, taking into consideration the occurrence of differences in communication time in such asynchronous communication. In particular, communication messages that always have the same timing are specified and used for assist force calculation, taking into consideration the timing of the maximum and minimum timestamps. This suppresses the influence of fluctuations in communication time in asynchronous communication.

[0024] [Timing chart] The processing timing of communication messages according to this embodiment will be described below with reference to the timing chart of Fig. 3. Here, three cases (cases A, B, and C) will be described as examples. First, the premise of asynchronous communication according to this embodiment will be described.

[0025] First, in order to control the EPS 100, the processing unit 204 performs input processing, calculation processing (=signal processing+assist force calculation processing), current control processing, and diagnosis processing. The input processing is a process of transferring a communication message received by the receiving circuit 201 and stored in the register 202 to the memory 205. In the example of Fig. 3, the time required for the input processing (lower diagonal stripe portion) is set to 25 μs.

[0026] The calculation process includes signal processing and assist force calculation processing, which will be described collectively as being performed consecutively. The signal processing identifies a communication message to be used for the assist force calculation process from among the communication messages stored in the memory 205, and converts the message into a format to be used in the assist force calculation process. In this embodiment, the signal processing performs linear interpolation (interpolation) using data (torque values) indicated by the two communication messages to estimate a torque value at a predetermined timing. The assist force calculation process calculates a control value for torque control using the motor 103 using the torque value estimated by the signal processing. In the example of FIG. 3, the time required for the calculation process (part A in the lower part) is set to 150 μs.

[0027] The current control process controls the current for controlling the motor 103 based on the assist force obtained by the calculation process. In the example of Fig. 3, the time required for the current control process (part C in the lower part) is set to 75 µs.

[0028] The diagnostic processes (D1 to D6 in the lower row) include various diagnostic processes related to the operation of the EPS 100, and six different types of diagnostic processes are shown here as an example. In the example of Fig. 3, the time required for a diagnostic process is 0.5 ms, and six types of diagnostic processes are executed during the calculation process. Note that the types and number of diagnostic processes and the time required for each diagnostic process are merely examples and are not limited to these.

[0029] In this embodiment, the processing cycle of each process on the processing unit 204 side is defined as follows. Input processing: 500μs cycle Calculation processing (= signal processing + assist force calculation processing): 1 ms cycle Current control process: 250μs cycle Diagnostic processing: 1 ms cycle

[0030] In FIG. 3, the horizontal axis is time [μs], and the start timing of the input processing is shown as the reference time "0". If the start timing of the arithmetic processing (signal processing) immediately after the reference time "0" is t (=75 μs), the time interval between the input processing and the arithmetic processing (signal processing) is T1. In other words, the start timing of the input processing is (t-T1). A negative value of the time indicates a past value based on the reference time "0". In the input processing, the time when the communication message and the timestamp stored in the register 202 are transferred to the memory 205 and stored is slightly delayed from the start timing of the input processing. The reference time "0" may be the time when the communication message is transferred to the memory 205 and stored, instead of the start timing of the input processing. The time t may also be the time when the time is obtained from the timer 203 slightly delayed from the start timing, instead of the start timing of the arithmetic processing (signal processing). These timings are expressed as the time of the input processing (memory transfer and storage process of the communication message and the timestamp) and the time of the signal processing.

[0031] Also, the memory 205 is provided with a data area capable of storing three communication messages of SENT communication that can be used for assist force calculation. For convenience, the three data areas are indicated as memory [0], [1], and [2]. In the data area, the communication messages of SENT communication and the timestamps at the time when the communication messages start to be received are stored in association with each other. In FIG. 3, the timing indicated by the timestamps corresponding to the communication messages is indicated by △. Furthermore, the torque value included in the communication message is the torque value detected by the torque sensor 102 at a time slightly shifted either before or after the time when the reception started. That is, the torque value at the timing close to the timing indicated by △ is included in the communication message. Furthermore, in FIG. 3, the arrows indicate that each communication message and its corresponding timestamp are transferred from the register 202 to the data area of ​​the memory 205. In FIG. 3, the timestamps are indicated as Timestamps, and the communication messages are indicated as Data. Next, each of the three cases will be described. Note that the times of the timestamps shown below are approximate values.

[0032] (Case A) 3, three communication messages (k-2) to (k) and a communication message being received are shown. In the lower example, four communication messages (k-3) to (k) and a communication message being received are shown. At the reference time "0", the communication message corresponding to the most recent torque value detected by the torque sensor 102 has not yet been received, that is, has not yet been stored in the register 202. Here, a case is shown in which the communication time for each communication message is Smax, and a case in which the communication time for each communication message is Smin are shown.

[0033] When the communication time is Smax in either case, in the input process of the reference time "0", data is stored in the three data areas of the memory as follows. Memory [0]: Communication message (k-2), timestamp (k-2) = -2150 [μs] Memory [1]: Communication message (k-1), timestamp (k-1) = -1620 [μs] Memory [2]: Communication message (k), timestamp (k) = -1080 [μs]

[0034] When the communication time is Smin in either case, in the input process of the reference time "0", data is stored in the three data areas of the memory as follows. Memory [0]: Communication message (k-2), timestamp (k-2) = -1750 [μs] Memory [1]: Communication message (k-1), timestamp (k-1) = -1310 [μs] Memory [2]: Communication message (k), timestamp (k) = -880 [μs]

[0035] (Case B) 3, four communication messages (k-3) to (k) and a communication message being received are shown. At the reference time "0", the reception of the communication message corresponding to the most recent torque value detected by the torque sensor 102 is incomplete, that is, the message is not yet stored in the register 202. Here, a case is shown in which the communication time of each communication message is time S (Smax>S>Smin).

[0036] In this case, in the input process of the reference time "0", data is stored in the three data areas of the memory as follows: Memory [0]: Communication message (k-2), timestamp (k-2) = -1800 [μs] Memory [1]: Communication message (k-1), timestamp (k-1) = -1300 [μs] Memory [2]: Communication message (k), timestamp (k) = -800 [μs]

[0037] (Case C) In the upper example of case C shown in Fig. 3, four communication messages (k-3) to (k) are shown. At reference time "0", the communication message (k) corresponding to the most recent torque value detected by torque sensor 102 has been completely received and is stored in register 202, and is in a state where it can be transferred to memory 205 in the immediately following input process. In other words, this is the state before it is stored in register 202. In this case, in the input process at reference time "0", data is stored in the three data areas of the memory as follows: Memory [0]: Communication message (k-2), timestamp (k-2) = -1620 [μs] Memory [1]: Communication message (k-1), timestamp (k-1) = -1080 [μs] Memory [2]: Communication message (k), timestamp (k) = -540 [μs]

[0038] In the lower example of case C shown in Fig. 3, five communication messages (k-4) to (k) are shown. At reference time "0", the communication message (k) corresponding to the most recent torque value detected by torque sensor 102 has been completely received and is stored in register 202, and is in a state where it can be transferred to memory 205 in the immediately following input process. In other words, this is the state before it is stored in register 202. In this case, in the input process at reference time "0", data is stored in the three data areas of the memory as follows: Memory [0]: Communication message (k-2), timestamp (k-2) = -1320 [μs] Memory [1]: Communication message (k-1), timestamp (k-1) = -880 [μs] Memory [2]: Communication message (k), timestamp (k) = -440 [μs]

[0039] In each of the above cases, the times (positions of △) indicated by the time stamps associated with the communication messages stored in the memory 205 are different from each other. In other words, the time when the sensor value used in the arithmetic processing at time t was acquired varies due to fluctuations in communication time and the processing cycle of the receiving side.

[0040] In this embodiment, a certain predetermined timing is set based on the reference time for communication messages used in the calculation process (signal processing) that starts immediately after the reference time "0". Then, data (torque value) corresponding to the certain timing is identified by interpolation based on communication messages having timestamps immediately before and after the certain timing.

[0041] In this embodiment, the predetermined timing is defined as follows. Given timing = (t-T1-T2) T2 = Smax × 2 + α (Smax × 2 <T2<Smax×3) t: signal processing time T1: Time interval between the time of input processing (memory transfer and storage processing of communication messages and time stamps) and the time of signal processing α: fixed parameter Smax: Maximum communication time for asynchronous communication (SENT communication) It should be noted that α may be set taking into consideration delays and variations in processing timing.

[0042] In the example of FIG. 3, when (t-T1)=0, the parameters can be set as follows: T1: 75 [μs] α: 22 [μs] Smax: 539 [μs] T2=Smax×2+α=539×2+22=1100[μs] Predetermined timing = -T2 = -1100 [μs]

[0043] Based on the above-mentioned predetermined timing, the communication message stored in the memory 205 is identified. The timestamps stored in the three data areas of the memory are compared with the predetermined timing, and two memories immediately before and after the predetermined timing are identified. In each of the above cases, the communication message is identified as follows.

[0044] (In the above example of Case A) Data(k-1) of communication message(k-1), timestamp(k-1)=-1620[μs] Data(k) of communication message(k), timestamp(k)=-1080[μs]

[0045] (In the example below for Case A) Data(k-1) of communication message(k-1), timestamp(k-1)=-1310[μs] Data(k) of communication message(k), timestamp(k) = -880[μs]

[0046] (Case B) Data(k-1) of communication message(k-1), timestamp(k-1)=-1300[μs] Data(k) of communication message(k), timestamp(k) = -800[μs]

[0047] (In the above example of Case C) Data(k-2) of communication message (k-2), timestamp(k-2)=-1620[μs] Data(k-1) of communication message(k-1), timestamp(k-1)=-1080[μs]

[0048] (In the example below for Case C) Data(k-2) of communication message (k-2), timestamp(k-2) = -1320[μs] Data(k-1) of communication message(k-1), timestamp(k-1)=-880[μs]

[0049] Furthermore, in the calculation process (signal processing) that starts immediately after the reference time "0", linear interpolation (interpolation) is performed using the data of the two selected communication messages to derive the torque value Data corresponding to the above-mentioned predetermined timing. The linear interpolation here can be defined as follows:

[0050]

number

[0051] That is, in the assist force calculation process shown in Fig. 3, the assist force is derived using the torque value obtained by the above-mentioned interpolation. Since the torque sensor 102 is duplicated as shown in Fig. 1, a torque value at a predetermined timing is derived corresponding to each detection value. These torque values ​​may then be used to derive a control value for the final assist force by performing averaging, noise removal, and the like.

[0052] [Calculation example] An example of control according to this embodiment will be described with reference to Figs. 4 to 6. In Figs. 4 to 6, the horizontal axis indicates time [s], and the vertical axis indicates signal value. Each diagram shows torque values ​​indicated by received data and torque values ​​obtained by interpolation based on the received data. Each data is plotted at the timing at which it was acquired (the time indicated by the timestamp and a specified timing), and each is connected by a straight line.

[0053] 4 shows an example of a signal in which a sine wave having a certain fundamental frequency and fundamental amplitude is superimposed with a sine wave having a frequency higher than the fundamental frequency and an amplitude smaller than the fundamental amplitude, simulating noise. As shown in FIG. 4, the torque value indicated by the received data and the torque value obtained by the interpolation can show almost the same value. Therefore, when the assist force is derived based on the interpolation, it is possible to realize a control amount equivalent to that in the case where the assist force is derived based on the received data, i.e., the value detected by the torque sensor 102 itself.

[0054] 5 and 6 show another example of the relationship between the torque value indicated by the received data and the torque value obtained by interpolation. FIG. 6 is an enlarged view of the time t1 in FIG. 5. As an example, the time t1 is set as the timing of the assist force calculation process. At this time t1, the received data 601 cannot be used for the assist force calculation process because the reception of the data has not been completed.

[0055] In this case, first, the received data 602 and the received data 603 are identified by the above-mentioned process, and then the torque value 604 is derived by interpolation. Then, in the assist force calculation process at time point t1, the assist force is calculated using the torque value 604. As a result, as shown in Fig. 5, it is possible to stabilize the communication delay due to asynchronous communication, that is, to make it approximately constant, while deriving a value equivalent to the torque value indicated by the received data by interpolation.

[0056] As described above, this embodiment makes it possible to derive a control value while suppressing the influence of fluctuations in communication time in asynchronous communication. For example, in an electric power steering device, it is possible to suppress delays (deviations) in the control value caused by fluctuations in communication time, and it is possible to suppress an uncomfortable feeling felt by the operator when steering. In addition, it is possible to derive a control value, i.e., an assist force, with the same accuracy as when the value detected by the torque sensor is used as is.

[0057] <Other embodiments> In the above embodiment, an EPS has been described as an example of a motor control device. However, the present invention can be applied to other devices, and may be applied to devices including a motor, such as an electric actuator device with a linear motion mechanism. Also, for example, the present invention may be used in an electric actuator device that controls the brakes of a vehicle.

[0058] In addition, in the present invention, a program or application for realizing the functions of the above-mentioned embodiments can be supplied to a system or device via a network or a storage medium, etc., and one or more processors in a computer of the system or device can read and execute the program.

[0059] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these are included in the scope of protection sought.

[0060] As described above, the present specification discloses the following: (1) An electric power steering device (e.g., 100), A torque sensor (e.g., 102) that detects a torque value around a steering shaft of a mechanism (e.g., 101); A receiving circuit (e.g., 201) that receives a communication message including a torque value detected by the torque sensor using asynchronous communication; A memory (e.g., 205) to which data corresponding to a communication message received by the receiving circuit and a time stamp indicating the time of the reception is transferred and stored; a derivation means (e.g., 204) for deriving a torque value at a predetermined timing by performing interpolation using two communication messages associated with time stamps having values ​​before and after a predetermined timing set based on a time of a derivation process for deriving a torque value used in a periodically executed assist force calculation process, among the communication messages stored in the memory; A processing means (e.g., 204) that performs a calculation process of the assist force for the mechanism unit using the torque value derived by the derivation means; An electric power steering device having the same. According to this configuration, in an electric power steering device configuration using asynchronous communication, it is possible to realize control that suppresses the effect on the steering feel by the operator.

[0061] (2) The electric power steering device according to (1), wherein the predetermined timing is defined by the following formula: Given timing = (t-T1-T2) T2 = Smax × 2 + α (Smax × 2 <T2<Smax×3) t: time of derivation process T1: The time interval between the time of data memory transfer storage processing and the time of derivation processing α: fixed value Smax: Maximum communication time for asynchronous communication According to this configuration, the communication message for calculating the assist force can be stably identified and used at a predetermined timing, and fluctuations in communication time of asynchronous communication can be suppressed.

[0062] (3) when the receiving circuit completes receiving one communication message using the asynchronous communication, the receiving circuit stores the communication message in a register (e.g., 202) in association with a timestamp indicating the time of receiving the communication message; The electric power steering device according to (1) or (2), wherein the information stored in the register is transferred to the memory by an input process that is periodically executed. According to this configuration, it is possible to realize control of the electric power steering device by taking into consideration the timing of the periodic transfer process of the communication message from the register to the memory.

[0063] (4) The electric power steering device according to any one of (1) to (3), wherein the memory is configured to include a data area capable of storing at least three pairs of data each consisting of a communication message and a time stamp. According to this configuration, it is possible to control the electric power steering device with a minimum memory storage area that has a data area capable of storing at least three pairs of data each consisting of a communication message and a timestamp.

[0064] (5) The electric power steering device according to any one of (1) to (4), wherein the asynchronous communication is SENT (Single Edge Nibble Transmission) communication. According to this configuration, it becomes possible to control the electric power steering device by using SENT communication as asynchronous communication.

[0065] (6) the torque sensor is multiplexed; The derivation means is Deriving a plurality of torque values ​​using each of the plurality of communication messages detected by the multiplexing; The electric power steering device according to any one of (1) to (5), further comprising: performing at least one of noise removal and averaging processing using the multiple torque values ​​to derive a torque value used in the assist force calculation processing. According to this configuration, it is possible to derive a torque value for more accurate assist force calculation processing by using the values ​​of the multiplexed torque sensors.

[0066] (7) a torque sensor (e.g., 102) for detecting a torque value around a steering shaft of a mechanism (e.g., 101); A receiving circuit (e.g., 201) that receives a communication message including a torque value detected by the torque sensor using asynchronous communication; A memory (e.g., 205) to which data corresponding to a communication message received by the receiving circuit and a time stamp indicating the time of the reception is transferred and stored; A control method for an electric power steering device (e.g., 100) including: a derivation step of deriving a torque value at a predetermined timing by performing interpolation using two communication messages associated with time stamps having values ​​before and after a predetermined timing set based on a time of a derivation process for deriving a torque value used in a periodically executed assist force calculation process, among the communication messages stored in the memory; a processing step of performing a calculation process of the assist force for the mechanism unit using the torque value derived in the derivation step; A control method for an electric power steering device having the above-mentioned configuration. According to this configuration, in an electric power steering device configuration using asynchronous communication, it is possible to realize control that suppresses the effect on the steering feel by the operator. [Explanation of symbols]

[0067] 100…EPS(Electric Power Steering) 101... Mechanism section 102...Torque sensor 103...Motor 200...ECU(Electronic Control Unit) 201...Receiving circuit 202...Register 203…Timer 204... Processing section 205…Memory

Claims

1. An electric power steering device, A torque sensor that detects a torque value around a steering shaft of the mechanism; a receiving circuit that receives a communication message including a torque value detected by the torque sensor using asynchronous communication; a memory for storing data in which a communication message received by the receiving circuit is associated with a timestamp indicating the time of reception of the message; a derivation means for deriving a torque value at a predetermined timing by performing interpolation using two communication messages associated with time stamps having values ​​before and after a predetermined timing set based on a time of a derivation process for deriving a torque value used in a periodically executed assist force calculation process, among the communication messages stored in the memory; and a processing means for performing a calculation process of the assist force for the mechanical portion by using the torque value derived by the derivation means; An electric power steering device having the same.

2. 2. The electric power steering device according to claim 1, wherein the predetermined timing is defined by the following formula: Predetermined timing=(t−T1−T2) T2=Smax×2+α (Smax×2<T2<Smax×3) t: time of derivation process T1: the time interval between the time of the data memory transfer storage process and the time of the derivation process α: fixed value Smax: Maximum communication time for asynchronous communication

3. the receiving circuit, when completing reception of one communication message using the asynchronous communication, stores the communication message in a register in association with a timestamp indicating a time related to reception of the communication message; 2. The electric power steering apparatus according to claim 1, wherein the information stored in the register is transferred to the memory by an input process that is periodically executed.

4. 2. The electric power steering apparatus according to claim 1, wherein the memory is configured to include a data area capable of storing at least three pairs of data each including a communication message and a time stamp.

5. The electric power steering device according to claim 1 , wherein the asynchronous communication is Single Edge Nibble Transmission (SENT) communication.

6. The torque sensor is multiplexed; The derivation means is Deriving a plurality of torque values ​​using each of the plurality of communication messages detected by the multiplexing; The electric power steering device according to claim 1 , further comprising: a step of performing at least one of noise removal and averaging processing using the plurality of torque values ​​to derive a torque value used in the assist force calculation processing.

7. A torque sensor that detects a torque value around a steering shaft of the mechanism; a receiving circuit that receives a communication message including a torque value detected by the torque sensor using asynchronous communication; a memory for storing data in which a communication message received by the receiving circuit is associated with a timestamp indicating the time of reception of the message; A control method for an electric power steering device, comprising: a derivation step of deriving a torque value at a predetermined timing by performing interpolation using two communication messages associated with time stamps having values ​​before and after a predetermined timing set based on a time of a derivation process for deriving a torque value used in a periodically executed assist force calculation process, among the communication messages stored in the memory; a processing step of performing a calculation process of the assist force for the mechanism unit using the torque value derived in the derivation step; A control method for an electric power steering device having the above-mentioned configuration.

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