JP2007333657A - Steering angle detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering angle detector which eliminates the need for storing the absolute steering angle and neutral position of a steering shaft, when the ignition switch is pulled out. <P>SOLUTION: The steering angle detector comprises a first resolver sensor for outputting n times periodic waveform signals, when a steering handle is rotated from a left steering limit position -θmax to the right steering limit position +θmax, a second resolver sensor for outputting the periodic waveform signals (n+1) times, and a third resolver sensor for outputting the periodic waveform signals (n+2) times. On the basis of the relative angle difference θcb between a relative angle θc, obtained by the third resolver sensor and a relative angle θb obtained by the second resolver sensor and the relative angle difference θca between a relative angle θc obtained by the third resolver sensor and a relative angle θa obtained by the first resolver sensor, the absolute steering angle θ and the neutral position are calculated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steering angle detection device that detects an absolute angle of a steering member using a resolver sensor.

  Conventionally, a technique for detecting an absolute angle (absolute rudder angle) of a steering shaft of a vehicle using a resolver sensor is known. For example, in the vehicle steering device proposed in Patent Document 1, a pair of resolver sensors provided on the steering shaft and rotation of the steering shaft at a lock position provided at equal intervals around the steering shaft when the ignition key is removed. And a locking mechanism for regulating. Further, in order to detect the absolute angle of the steering shaft, the shaft multiples of the output signals of the pair of resolver sensors are set to m ×, n × (m> n), respectively, and the number N of lock positions around the steering shaft is set. , (Mn) ≦ N.

In this configuration, by taking the difference between the output signals of the pair of resolver sensors, it is possible to obtain a periodic waveform signal that is repeated every time the steering shaft rotates 360 ° / (mn). In this case, in a situation where the ignition key is removed and the steering shaft is restricted from rotation by the lock mechanism, the output of the periodic waveform signal does not become the same level value at different angles within the restriction angle region where the steering shaft can rotate. .
Therefore, by storing the absolute angle of the steering shaft at the time when the ignition key is removed, the absolute value of the steering shaft is calculated from the relationship between the stored absolute angle and the current rotational angle position of the steering shaft at the next vehicle operation. The angle can be detected.

Patent Document 2 proposes a steering angle detection device that stores a neutral position of a steering shaft in a steering angle sensor and detects a steering angle by measuring a rotation angle based on the neutral position with a steering angle sensor. Has been. In this apparatus, the neutral position is stored in the steering angle sensor in the steering assembly process, but the stored neutral position may be shifted. Therefore, the neutral position shift is detected based on the absolute rotation angle within one rotation of the electric motor used in the electric power steering apparatus, and updated and stored in the correct neutral position.
JP 2003-269953 A JP 2004-168191 A

However, in the apparatus of Patent Document 1, the lock mechanism becomes complicated. It is also necessary to memorize the steering angle at the time when the ignition key is removed. For this reason, it is necessary to provide a configuration capable of storing and holding the memory even when the power battery is removed.
Moreover, in the apparatus of patent document 2, it is necessary to memorize | store a neutral position correctly in an assembly | attachment process, and a manufacturing man-hour will increase. In addition, processing such as neutral position deviation correction is required.

  The present invention has been made to address the above problems, and an object thereof is to provide a steering angle detection device that does not need to store the absolute angle or neutral position of the steering shaft.

  In order to achieve the above object, the present invention is characterized in that a first resolver sensor that outputs a periodic waveform signal n times when a steering member is steered from a left steering limit position to a right steering limit position, and a left steering limit position When the steering member is steered from the right steering limit position to the right steering limit position, the second resolver sensor that outputs (n + 1) periodic waveform signals and when the steering member is steered from the left steering limit position to the right steering limit position (n + 2) A third resolver sensor that outputs a periodic waveform signal, and a difference between a signal output value of the first resolver sensor and a signal output value of the second resolver sensor, or a signal output value of the second resolver sensor and the above Based on the difference from the signal output value of the third resolver sensor, a characteristic in which one peak value appears with respect to the change of the steering angle in the steerable range from the left steering limit position to the right steering limit position. Based on the difference between the signal output value of the first resolver sensor and the signal output value of the third resolver sensor based on the first electrical angle calculation means for calculating the first electrical angle, and the right steering from the left steering limit position. Calculated by a second electrical angle calculating means for calculating a second electrical angle having a characteristic in which two peak values appear with respect to a change in the steering angle in a steerable range up to the limit position, and calculated by the first electrical angle calculating means. Absolute steering angle calculating means for calculating a neutral position and an absolute steering angle of the steering member based on the first electrical angle and the second electrical angle calculated by the second electrical angle calculating means; It is in.

  According to this invention, when the steering member is steered from the left steering limit position to the right steering limit position, the first resolver sensor generates n periodic waveform signals, and the second resolver sensor outputs (n + 1) periodic waveform signals. The third resolver sensor outputs (n + 2) number of periodic waveform signals. Therefore, by calculating the difference between the signal output value of the first resolver sensor and the signal output value of the second resolver sensor, or the difference between the signal output value of the second resolver sensor and the signal output value of the third resolver sensor, In the steerable range from the left steering limit position to the right steering limit position, it is possible to obtain an electrical angle having a characteristic in which one peak value having no periodicity appears with respect to a change in the steering angle. The first electrical angle calculation means calculates this electrical angle as the first electrical angle.

Further, by obtaining the difference between the signal output value of the first resolver sensor and the signal output value of the third resolver sensor, the change in the steering angle in the steerable range from the left steering limit position to the right steering limit position is detected. An electrical angle having a characteristic in which two peak values appear can be obtained. The second electrical angle calculation means calculates this electrical angle as the second electrical angle.
The absolute rudder angle calculating means calculates the neutral position of the steering member based on the first electric angle calculated by the first electric angle calculating means and the second electric angle calculated by the second electric angle calculating means. The absolute rudder angle is calculated.

The second electrical angle calculated by the second electrical angle calculation means appears as a periodic waveform signal for two cycles with respect to the change in the steering angle within the steerable range. Therefore, the neutral position of the steering member can be obtained by calculating the boundary of the periodic waveform signal (the boundary between the first period and the second period). For example, when the second electrical angle is output as a periodic waveform signal that changes in a sawtooth shape with respect to a change in the steering angle, the steering member is in a neutral position when the passage of a triangular vertex in the sawtooth shape signal is detected. Can be determined to exist.
Therefore, the neutral position can be detected accurately and simply. Further, since the neutral position can be detected during the steering of the steering member, it is not necessary to store the neutral position in the manufacturing process, and the number of manufacturing steps can be reduced.

On the other hand, the first electrical angle calculated by the first electrical angle calculation means changes without periodicity due to the phase difference of the periodic waveform signal output from the resolver sensor, and the position of the steering member (absolutely over the steerable range). (Steering angle) and a one-to-one value.
Therefore, the absolute steering angle of the steering member can be calculated from the first electrical angle. In this case, for example, the absolute steering angle can be detected with higher accuracy by combining the first electrical angle and the second electrical angle.
Since the second electrical angle outputs a periodic waveform signal for one cycle in each of the two regions of the right steering region on the right steering side and the left steering region on the left steering side from the neutral position, the second electrical angle is compared with the first electrical angle. The output change with respect to the change of the steering angle is large. The value of the second electrical angle corresponds to the position of the steering member (absolute steering angle) on a one-to-one basis in the two steering regions. Therefore, the detection accuracy can be improved by specifying the steering region based on the first electrical angle and detecting the absolute steering angle from the value of the second electrical angle in the specified steering region.
Further, since the absolute rudder angle is calculated during the steering of the steering member, it is not necessary to store the absolute rudder angle until the next driving run. Accordingly, the consumption of dark current of the storage device can be reduced.

  Another feature of the present invention is that the absolute steering angle calculating means is configured such that when the value of the first electrical angle is not zero and the value of the second electrical angle is zero, the steering wheel is in a neutral position. It is to be determined that there is.

  The second electrical angle is calculated based on the difference between the signal output value of the first resolver sensor and the signal output value of the third resolver sensor. The two signal output values are the same at the neutral position in the steerable range. Value. These two signal output values are the same at the steering limit angle position in addition to the neutral position. Therefore, by detecting that the value of the first electrical angle is not zero and the value of the second electrical angle is zero, the neutral position of the steering member can be easily obtained with high accuracy.

  Another feature of the present invention is that the absolute rudder angle calculating means determines whether the steering position of the steering member is in the right steering area based on the magnitude relationship between the first electric angle and the second electric angle. And determining the absolute steering angle based on the region determination result and the value of the second electrical angle.

The second electrical angle takes a value corresponding to the position of the steering member (absolute rudder angle) on a one-to-one basis in the two regions of the right steering region on the right steering side and the left steering region on the left steering side from the neutral position. The output change with respect to the change of the steering angle is larger than that of the first electrical angle. Therefore, if the steering area of the steering member is known, a highly accurate absolute steering angle can be calculated from the value of the second electrical angle. On the other hand, the magnitude relationship between the first electrical angle and the second electrical angle differs depending on the left and right steering areas.
Therefore, the absolute rudder angle calculating means determines the steering region where the steering member is located based on the magnitude relationship between the first electrical angle and the second electrical angle, and from the value of the second electrical angle in the determined steering region. Calculate the absolute rudder angle. As a result, the absolute steering angle can be calculated with high accuracy.

  Another feature of the present invention is that abnormality detection means for detecting an abnormality in the first resolver sensor, the second resolver sensor, and the third resolver sensor, and an abnormality in one resolver sensor among the three resolver sensors are detected. In some cases, there is provided an abnormal-time absolute rudder angle calculating means for calculating an absolute rudder angle of the steering member based on a difference between signal output values of two resolver sensors in which no abnormality is detected.

  According to this, even if one resolver sensor fails, the absolute steering angle of the steering member is calculated by the other resolver sensor, so that the safety of the vehicle is improved.

  Another feature of the present invention is that the abnormal absolute steering angle calculation means is based on the transition of the second electrical angle calculated by the second electrical angle calculation means when an abnormality of the second resolver sensor is detected. Then, it is determined whether the steering position of the steering member is in the right steering region or the left steering region, and the steering angle is calculated based on the region determination result and the value of the second electrical angle.

  Since the first electrical angle cannot be calculated when the second resolver sensor is abnormal, it is necessary to calculate the absolute steering angle only from the second electrical angle. The second electrical angle appears as a periodic waveform signal for two cycles with respect to the change of the steering angle in the steerable range. Therefore, the steering region where the steering member is located can be determined by detecting the transition of the second electrical angle.

  For example, when the second electrical angle is output as a periodic waveform signal that changes in a sawtooth shape with respect to a change in the steering angle, the steering member is in a neutral position when the passage of a triangular vertex in the sawtooth shape signal is detected. Can be determined to have passed. Further, the change in the signal output of the second electrical angle is different between when the steering is performed in the right direction and passed through the neutral position and when the steering is performed in the left direction and passes through the neutral position. Accordingly, the steering region where the steering member is located can be determined from the transition of the second electrical angle.

The abnormal absolute steering angle calculation means calculates the steering angle based on the steering region determination based on the transition of the periodic waveform signal of the second electrical angle and the value of the second electrical angle, using such a principle.
Therefore, even if the second resolver sensor fails, the steering angle can be calculated with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a vehicle steering apparatus provided with a steering angle detection apparatus as one embodiment.

  This vehicle steering device mechanically includes a steering operation device 10 that is steered by a driver, and a steering device 20 that steers left and right front wheels FW1 and FW2 as steered wheels according to the steering operation of the driver. A separate steer-by-wire system is used. The steering operation device 10 includes a steering handle 11 as an operation unit that is rotated by a driver. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and a steering reaction force electric motor 13 is assembled to the lower portion of the steering input shaft 12. The steering reaction force electric motor 13 drives the steering input shaft 12 to rotate about the axis via the speed reduction mechanism 14.

  The steered device 20 includes a rack bar 21 that extends in the left-right direction of the vehicle. The left and right front wheels FW1, FW2 as steered wheels are connected to both ends of the rack bar 21 via a tie rod and a knuckle arm (not shown) so as to be steerable. The left and right front wheels FW1, FW2 are steered to the left and right by the displacement of the rack bar 21 in the axial direction. On the outer periphery of the rack bar 21, a steering electric motor 22 assembled in a housing (not shown) is provided. The rotation of the steered electric motor 22 is decelerated by the screw feed mechanism 23 and is converted into an axial displacement of the rack bar 21. The steering device 20 also has a steering output shaft 24 that can rotate around the axis. A pinion gear 25 is fixed to the lower end of the steering output shaft 24. The pinion gear 25 meshes with rack teeth 21a provided on the rack bar 21, and the rack bar 21 is axially rotated by rotation around the axis of the steering output shaft 24. It is displaced to.

  A cable 31 as an intermediate member is disposed between the steering input shaft 12 and the steering output shaft 24. The cable 31 transmits the rotation around the axis of the steering input shaft 12 to the steering output shaft 24. A first electromagnetic clutch 32 is disposed between the fixing member 31 a at the upper end of the cable 31 and the lower end of the steering input shaft 12. The first electromagnetic clutch 32 is set in a disconnected state in an energized state to disconnect the cable 31 and the steering input shaft 12 so that power cannot be transmitted, and is set in a connected state in a non-energized state to set the cable 31 and the steering input shaft 12. And are connected so that power can be transmitted. A second electromagnetic clutch 33 is disposed between the fixing member 31 b at the lower end of the cable 31 and the upper end of the steering output shaft 24. The second electromagnetic clutch 33 is set in a disconnected state in an energized state to disconnect the cable 31 and the steering output shaft 24 so that power cannot be transmitted, and is set in a connected state in a non-energized state to set the cable 31 and the steering output shaft 24. And are connected so that power can be transmitted.

Next, the electric control device 40 that controls the steering reaction force electric motor 13, the steering electric motor 22, and the electromagnetic clutches 32 and 33 will be described.
The electric control device 40 includes a steering angle detection device 50 for detecting the steering angle θ of the steering handle 11, a steering reaction force electronic control unit (hereinafter referred to as a steering reaction force ECU) 60, and front wheel steering electronics. And a control unit (hereinafter referred to as front wheel steering ECU) 70.

The steering angle detection device 50 includes a first resolver sensor 51, a second resolver sensor 52, a third resolver sensor 53, and an absolute angle detection arithmetic device (hereinafter referred to as an absolute angle detection ECU) 54. The
The first resolver sensor 51 includes a first resolver 51s provided at an intermediate portion of the steering input shaft 12, and a first relative angle detection circuit 51c that detects a relative angle θa from an output signal of the first resolver 51s.
The second resolver sensor 52 includes a second resolver 52s provided at an intermediate portion of the steering input shaft 12 along with the first resolver 51s, and a second relative angle detection circuit that detects a relative angle θb from an output signal of the second resolver 52s. 52c.
The third resolver sensor 53 includes a third resolver 53s provided in an intermediate portion of the steering input shaft 12 along with the second resolver 52s, and a third relative angle detection circuit that detects the relative angle θc from the output signal of the third resolver 53s. 53c.

Each resolver 51s, 52s, 53s includes an annular resolver rotor 51sr, 52sr, 53sr and a resolver stator 51ss, 52ss, 53ss. In each resolver 51s, 52s, 53s, resolver rotors 51sr, 52sr, 53sr are fixed on the outer peripheral surface of the steering input shaft 12, and resolver stators 51ss, 52ss, 53ss are resolver rotors 51sr, 52sr on the inner peripheral surface thereof. , 53sr are fixed to the vehicle body so that the outer peripheral surfaces thereof face each other.
Each resolver 51s, 52s, 53s is provided with a primary winding (not shown) as an exciting coil in the resolver rotor 51sr, 52sr, 53sr, and a secondary winding as a detection coil in the resolver stator 51ss, 52ss, 53ss. A plurality of (not shown) are provided.

  Each of the relative angle detection circuits 51c, 52c, and 53c excites the primary windings of the resolvers 51s, 52s, and 53s with a sine wave signal, and generates an induced voltage signal based on the excitation signal from a plurality of secondary windings. input. When the steering input shaft 12 rotates and the positional relationship between the resolver stators 51ss, 52ss, 53ss and the resolver rotors 51sr, 52sr, 53sr of the resolvers 51s, 52s, 53s changes, the magnetic flux passing through the secondary winding changes. . Therefore, by comparing the phase difference between the sine wave voltage applied to the primary winding and the induced voltage acting on the secondary winding, the resolver stators 51ss, 52ss, 53ss and the resolver rotors 51sr, 52sr, 53sr are compared. A relative angular position can be detected.

The steering input shaft 12 is restricted from rotating about its axis by a stroke end (not shown). The rotatable range of the steering input shaft 12 is the same as the rotatable range of the steering handle 11. Hereinafter, this range is referred to as a steerable range.
In the present embodiment, the steerable range is set such that the neutral position of the steering handle 11 is “0” and the steering limit angle −θmax in the left direction to the steering limit angle + θmax in the right direction.

The first relative angle detection circuit 51c is configured to output a periodic waveform signal 11 times in the process in which the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax.
On the other hand, the second relative angle detection circuit 52c is configured to output 12 periodic waveform signals in the process in which the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax. The third relative angle detection circuit 53c is configured to output 13 periodic waveform signals in the process in which the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax.

  The number of outputs of the periodic waveform signal in the process in which the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax is not limited to the above-described values, but the relative angle detection circuits 51c and 52c. , 53c are set differently by “1”. Hereinafter, the number of outputs of the periodic waveform signal of the first relative angle detection circuit 51c is n times, the number of outputs of the second relative angle detection circuit 52c is (n + 1) times, and the number of outputs of the third relative angle detection circuit 53c is (n + 2). Explain as times.

  FIG. 8 shows periodic waveform signals output from the first relative angle detection circuit 51c, the second relative angle detection circuit 52c, and the third relative angle detection circuit 53c. The horizontal axis represents the steering angle θ (absolute steering angle θ) of the steering handle 11, and the vertical axis represents the electrical angle. In the figure, the signal waveform represented by a broken line represents the relative angle θa output from the first relative angle detection circuit 51c, and the signal waveform represented by a two-dot chain line represents the relative angle output from the second relative angle detection circuit 52c. A signal waveform in which θb is represented by a one-dot chain line represents a relative angle θc output from the third relative angle detection circuit 53c.

The relative angle θa is an electrical angle with an angle (2 · θmax / n) obtained by subtracting the steerable range by the value n as one cycle (2π), and the relative angle of the resolver rotor 51sr to the resolver stator 51ss of the first resolver 51s. Represents a specific position. Similarly, the relative angle θb is an electrical angle with an angle (2 · θmax / (n + 1)) obtained by subtracting the steerable range by a value (n + 1) as one cycle (2π), and the resolver stator of the second resolver 52s. This represents the relative position of the resolver rotor 52sr with respect to 52ss. Similarly, the relative angle θc is an electrical angle with an angle (2 · θmax / (n + 2)) obtained by subtracting the steerable range by a value (n + 2) as one cycle (2π), and the resolver stator of the third resolver 53s. This represents the relative position of the resolver rotor 53sr with respect to 53ss.
On the other hand, the absolute steering angle θ represents a mechanical rotation angle (rotation position) of the steering handle 11 with the neutral position of the steering handle 11 as “0” with reference to the neutral position.
In the following description, the output signal of the first relative angle detection circuit 51c representing the relative angle θa is called the output signal θa of the first resolver sensor 51, and the output signal of the second relative angle detection circuit 52c representing the relative angle θb is the first output signal. The output signal θb of the second resolver sensor 52 is called an output signal θb, and the output signal of the third relative angle detection circuit 53c representing the relative angle θc is called an output signal θc of the third resolver sensor 53.

As shown in FIG. 8, the periodic waveform signals θa, θb, θc output from the first resolver sensor 51, the second resolver sensor 52, and the third resolver sensor 53 are right-angled triangles having sides perpendicular to the horizontal axis. Appears as a multiple sawtooth signal. One peak of the sawtooth signal waveform is one cycle.
Each resolver sensor 51, 52, 53 is set such that its output is 0 radians in electrical angle when the steering handle 11 is turned to the left steering limit angle -θmax position, and the steering handle 11 is steered to the right. The output is set to be 2π radians when rotated to the limit angle + θmax position.

Each resolver sensor 51, 52, 53 is set so that the number of output of the periodic waveform signal differs only once in the process of rotating the steering handle 11 from the left steering limit angle −θmax to the right steering limit angle + θmax. Therefore, a phase difference occurs in the output (electrical angle) with respect to the steering angle θ.
In this case, there is no phase difference between the output signal θa of the first resolver sensor and the output signal θb of the second resolver sensor 52 when the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax.
Similarly, there is no phase difference between the output signal θb of the second resolver sensor 52 and the output signal θc of the third resolver sensor 53 when the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax.
On the other hand, the output signal θa of the first resolver sensor 51 and the output signal θc of the third resolver sensor 53 are at an intermediate position when the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax. Are also in phase. The intermediate position having the same phase corresponds to the neutral position of the steering handle 11.

  The output signals θa, θb, θc of the first resolver sensor 51, the second resolver sensor 52, and the third resolver sensor 53 are input to the absolute angle detection ECU 54. The absolute angle detection ECU 54 includes a microcomputer as a main part, and calculates the neutral position and the steering angle θ (absolute steering angle) of the steering wheel 11 using the relative angles θa, θb, and θc. The steering angle calculation process performed by the absolute angle detection ECU 54 will be described later.

The steering reaction force ECU 60 includes a microcomputer as a main part, and is a control device that generates an appropriate steering reaction force in response to a driver's steering operation. The steering reaction force ECU 60 is connected to the absolute angle detection ECU 54 and the vehicle speed sensor 41. . The vehicle speed sensor 41 outputs a detection signal indicating the vehicle speed V. The steering reaction force ECU 60 calculates a target steering reaction force based on the steering angle θ calculated by the absolute angle detection ECU 54 and the vehicle speed V detected by the vehicle speed sensor 41. In calculating the target steering reaction force, the steering reaction force table shown in FIG. 9 is referred to. This steering reaction force table is stored in the ROM of the steering reaction force ECU 60, and for each of a plurality of representative vehicle speed values, a plurality of target steering reaction force values that increase nonlinearly as the steering wheel steering angle θ increases. Is set.
Instead of using this steering reaction force table, a target steering reaction force value that changes according to the steering angle θ and the vehicle speed V is defined in advance by a function, and the target steering reaction force is calculated using the function. A value may be calculated.

The steering reaction force ECU 60 supplies a drive current corresponding to the calculated target steering reaction force to the steering reaction force electric motor 13 via a drive circuit (not shown). Thus, the target steering reaction force by the steering reaction force electric motor 13 is applied to the rotation operation of the steering handle 11, and the driver rotates the steering handle 11 while feeling an appropriate steering reaction force. it can.
The steering reaction force electric motor 13 uses a three-phase synchronous permanent magnet motor and is rotationally controlled by vector control described in a two-phase rotating magnetic flux coordinate system. In this case, it is necessary to input a signal synchronized with the motor rotation angle in order to perform the two-phase / three-phase conversion process. Therefore, the steering reaction force ECU 60 inputs one of the relative angle θa, the relative angle θb, and the relative angle θc as a synchronization signal from the absolute angle detection ECU 54.

The front-wheel steering ECU 70 is configured by a microcomputer as a main part, and is a control device that steers front wheels (steered wheels) at a steering angle corresponding to a driver's steering wheel operation. The absolute-angle detection ECU 54 and the vehicle speed sensor 41 The turning angle sensor 43 is connected.
The turning angle sensor 43 is assembled to the rack bar 21 and measures the axial displacement of the rack bar 21 to detect and output the actual turning angle δ of the left and right front wheels FW1 and FW2. Note that the actual turning angle δ represents the rightward turning angle of the left and right front wheels FW1, FW2 as a positive value with the neutral position of the left and right front wheels FW1, FW2 being “0”, and the left direction of the left and right front wheels FW1, FW2 The steering angle of is expressed as a negative value. Further, the turning angle sensor 43 may be configured to detect the actual turning angle δ by detecting the rotation angle of the steering output shaft 24.

  The front wheel steering ECU 70 calculates a target front wheel steering angle based on the steering wheel steering angle θ calculated by the absolute angle detection ECU 54 and the vehicle speed V detected by the vehicle speed sensor 41. In calculating the target front wheel turning angle, the turning angle table shown in FIG. 10 is referred to. This steering angle table is stored in the ROM of the front wheel steering ECU 70, and for each of a plurality of representative vehicle speed values, the target front wheel rotation for the standby wire that increases nonlinearly as the steering wheel steering angle θ increases. The rudder angle is set. The rate of change of the target front wheel turning angle with respect to the steering wheel steering angle θ is small within a small range of the absolute value | θ | of the steering wheel steering angle θ, and increases as the absolute value | θ | of the steering wheel steering angle θ increases. Is set. Instead of using this turning angle table, a function indicating the relationship between the steering wheel steering angle θ and the target front wheel turning angle is prepared in advance. The wheel turning angle may be calculated.

  The front wheel turning ECU 70 turns the vehicle through a drive circuit (not shown) using the steering angle difference so that the actual turning angle δ detected by the turning angle sensor 43 becomes equal to the final target front wheel turning angle. The rotation of the rudder electric motor 22 is controlled. As a result, the steering electric motor 22 is rotationally driven, drives the rack bar 21 in the axial direction via the screw feed mechanism 23, and steers the left and right front wheels FW1, FW2 to the target turning angle.

  Next, the steering angle detection process of the steering handle 11 performed by the steering angle detection device 50 will be described. First, an initial control routine performed when the vehicle is started will be described. FIG. 2 is a flowchart showing an initial control routine executed by the absolute angle detection ECU 54 when the vehicle is started. This process is stored as a control program in the ROM of the absolute angle detection ECU 54, and is executed when the ignition switch of the vehicle is turned on.

  When the ignition switch of the vehicle is turned on and this initial control routine is started, the absolute angle detection ECU 54 determines whether the first resolver sensor 51, the second resolver sensor 52, and the third resolver sensor 53 are all normal in step S11. Judge whether or not. This determination is made by checking the terminal voltage of the windings provided in each resolver 51s, 52s, 53s. When a wire breakage, short circuit, insulation failure, or the like occurs in the windings provided in the resolvers 51s, 52s, 53s, the winding terminal voltage is out of the reference range. Therefore, in this step S11, when the winding terminal voltage is detected by the first relative angle detection circuit 51c, the second relative angle detection circuit 52c, and the third relative angle detection circuit 53c, and the detected voltage is out of the reference range. The resolvers 51s, 52s, and 53s are determined to be abnormal.

  In detecting the abnormality of each resolver sensor 51, 52, 53, the absolute angle detection ECU 54 may detect the abnormality including the abnormality of the relative angle detection circuits 51c, 52c, 53c itself. For example, the voltage value of the periodic waveform signal output from the relative angle detection circuits 51c, 52c, and 53c may be checked by the absolute angle detection ECU 54, and it may be determined that the circuit is abnormal when the voltage value is out of the reference range. Further, the circuit abnormality may be determined from the waveforms of the output signals of the relative angle detection circuits 51c, 52c, and 53c.

When it is determined that the first resolver sensor 51, the second resolver sensor 52, and the third resolver sensor 53 are all normal (S11: YES), a first absolute steering angle calculation process is performed in step S12. The first absolute steering angle calculation process will be described later.
In addition, when any one of the first resolver sensor 51, the second resolver sensor 52, and the third resolver sensor 53 is detected (S11: NO), in step S13, the first electromagnetic clutch 32 and A connection command is output to the second electromagnetic clutch 33. In response to this connection command, the first electromagnetic clutch 32 connects the cable 31 and the steering input shaft 12 so that power can be transmitted. The second electromagnetic clutch 33 connects the cable 31 and the steering output shaft 24 so that power can be transmitted. As a result, the steering input shaft 12 and the steering output shaft 24 are coupled via the cable 31 so that power can be transmitted. Accordingly, the left and right front wheels FW1 and FW2 are set to be directly steered by the turning operation of the steering handle 11 performed by the driver.
When the process of step S12 or step S13 is completed in this way, this control routine is terminated.

  Next, an absolute steering angle calculation process after the initial control process is completed will be described. FIG. 3 is a flowchart showing an absolute steering angle calculation routine executed by the absolute angle detection ECU 54. This process is stored as a control program in the ROM of the absolute angle detection ECU 54, and is repeatedly performed at a predetermined short period after the initial control process is completed.

When this routine is started, the absolute angle detection ECU 54 determines in step S21 whether or not the first resolver sensor 51, the second resolver sensor 52, and the third resolver sensor 53 are all normal. This determination is an abnormality detection process similar to step S11 described above, but is repeatedly performed while the ignition switch of the vehicle is on.
And while the abnormality of the resolver sensors 51, 52, 53 is not detected, the first absolute steering angle calculation process is repeated (S22).

On the other hand, when an abnormality is detected in any of the resolver sensors 51, 52, 53, it is determined whether or not the first resolver sensor 51 is the only resolver sensor that becomes abnormal (S23). If only the resolver sensor 51 is detected abnormal (S23: YES), a second absolute steering angle calculation process is performed (S24).
If the determination in step S23 is “NO”, that is, it is not an abnormality of only the first resolver sensor 51, it is determined whether or not the only resolver sensor that becomes abnormal is only the third resolver sensor 53 (S25). When an abnormality is detected only in the third resolver sensor 53 (S25: YES), a third absolute steering angle calculation process is performed (S26).
If the determination in step S25 is “NO”, that is, if the abnormality is not only in the third resolver sensor 53, it is determined whether or not the only resolver sensor that is abnormal is only the second resolver sensor 52 (S27). If only the second resolver sensor 52 has detected an abnormality (S27: YES), a fourth absolute steering angle calculation process is performed (S28).

  Further, if the determination in step S27 is “NO”, that is, if an abnormality is detected in a plurality of resolver sensors among the three resolver sensors 51, 52, 53, the first electromagnetic clutch 32 and the second electromagnetic clutch 33 are detected. A connection command is output to (S29). Accordingly, the left and right front wheels FW1 and FW2 are set to be directly steered by the turning operation of the steering handle 11 performed by the driver.

  This control routine is repeatedly executed during operation of the vehicle. Therefore, when any of the resolver sensors 51, 52, 53 fails during traveling, the absolute steering angle calculation process corresponding to the failed resolver sensors 51, 52, 53 is selected. When a plurality of resolver sensors fail, the steering operation device 10 and the steering device 20 are mechanically connected without performing the absolute steering angle calculation process, and the left and right front wheels FW1 are operated by the driver's steering operation. , FW2 is directly steered.

  Next, the first absolute steering angle calculation process will be described. FIG. 4 is a flowchart showing a first absolute steering angle calculation routine executed by the absolute angle detection ECU 54. This first absolute steering angle calculation routine corresponds to the processing in step S12 in the above-described initial control routine and the processing in step S22 in the absolute steering angle calculation routine, and the control program is stored in the ROM of the absolute angle detection ECU 54. Is remembered as

  When this routine is started, the absolute angle detection ECU 54 reads the output signals θa, θb, and θc of the first resolver sensor 51, the second resolver sensor 52, and the third resolver sensor 53 in step S31. Subsequently, it is determined whether or not the relative angle θc is equal to or greater than the relative angle θb from the read signal (S32). If θc ≧ θb (S32: YES), the value obtained by subtracting θb from θc is set as a relative value. The angle difference is calculated as θcb (= θc−θb) (S33). On the other hand, if θc <θb (S32: NO), a value obtained by subtracting θb from θc and adding 2π is calculated as a relative angular difference θcb (= θc−θb + 2π) (S34).

  As shown in FIG. 8, in the process of rotating the steering handle 11 from the left steering limit angle −θmax to the right steering limit angle + θmax, the third resolver sensor 51 outputs (n + 2) times of the sawtooth signal θc, The resolver sensor 52 outputs (n + 1) number of sawtooth shape signals θb.

  Here, consider a case where the steering handle 11 is steered rightward from the position of the left steering limit angle −θmax. As for the phase difference between the output signal θc of the third resolver sensor 53 and the output signal θb of the second resolver sensor 52, when the position of the left steering limit angle −θmax is used as a reference (phase difference = 0), the phase difference progresses in the right steering direction. It increases to the maximum “2π” at the position of the right steering limit angle + θmax and returns to the same phase. Therefore, if the phase difference in the steerable range is known, the steering angle θ (absolute steering angle) can be obtained.

The processing in steps S33 and S34 calculates this phase difference, but the relative relationship between the relative angle θc and the relative angle θb is reversed in the middle. Therefore, when the magnitude relationship between the relative angle θc and the relative angle θb is reversed (θc <θb), 2π is added to the relative angle difference θcb.
Therefore, as shown by the solid line in FIG. 8, the relative angle difference θcb becomes the steering angle θ without periodicity in the process in which the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax. It increases linearly from “0” to “2π” in proportion. Accordingly, the steering angle θ of the steering handle 11 can be detected by obtaining the relative angle difference θcb.

  Next, the absolute angle detection ECU 54 determines whether or not the relative angle θc is equal to or greater than the relative angle θa in step S35. If θc ≧ θa (S35: YES), a value obtained by subtracting θa from θc is calculated as a relative angular difference θca (= θc−θa) (S36). On the other hand, if θc <θa (S35: NO), a value obtained by subtracting θa from θc and adding 2π is calculated as a relative angular difference θca (= θc−θa + 2π) (S37).

This process is a process for calculating the phase difference between the output signal θc of the third resolver sensor 53 and the output signal θa of the first resolver sensor 51.
As shown in FIG. 8, the first resolver sensor 51 outputs the sawtooth shape signal θa n times in the process of rotating the steering handle 11 from the left steering limit angle −θmax to the right steering limit angle + θmax. On the other hand, the third resolver sensor 53 outputs (n + 2) times of the sawtooth signal θc.
Therefore, the phase difference between the output signal θc of the third resolver sensor 53 and the output signal θa of the first resolver sensor 51 is as shown in FIG. 8 when the position of the left steering limit angle −θmax is used as a reference (phase difference = 0). As shown in the figure, it increases as it advances in the right steering direction, reaches the maximum “2π” at the middle position of the steerable range, returns to the same phase, and then increases again to reach the maximum “ 2π ”.

This phase difference can be expressed by a relative angle difference θca that is a difference between the relative angle θc and the relative angle θa, but the magnitude relationship between the two is reversed halfway. Therefore, when the magnitude relationship between the relative angle θc and the relative angle θa is reversed (θc <θa), 2π is added to the relative angle difference to obtain the relative angle difference θca.
As a result, the relative angle difference θca outputs a sawtooth-shaped two-cycle periodic waveform signal in the process of rotating the steering handle 11 from the left steering limit angle −θmax to the right steering limit angle + θmax, as shown in FIG. It will be. Therefore, if it can be identified whether the steering position of the steering handle 11 belongs to the right steering region or the right steering region, the absolute steering angle of the steering handle 11 can be detected from the relative angle difference θca.

After calculating the relative angle difference θca in step S36 or step S37, the absolute angle detection ECU 54 performs the determination process in step S38.
In this step S38, it is determined whether the relative angle difference θca is “0” (θca = 0) and the relative angle difference θcb is not “0” (θcb ≠ 0). As shown in FIG. 8, the relative angle difference θca becomes “0” when the steering wheel 11 is positioned at the left steering limit angle −θmax and at the neutral position. On the other hand, the relative angle difference θcb is “0” when the steering wheel 11 is positioned at the left steering limit angle −θmax.
Therefore, if “YES” is determined in step S38, it is determined that the steering angle θ (absolute rudder angle) of the steering handle 11 is “0”, that is, in the neutral position (S39).
In detecting the neutral position, for example, when the relative angle difference θca greatly fluctuates from “0” to “2π” or from “2π” to “0”, the steering wheel 11 is in the neutral position ( It may be determined that the steering angle θ = 0).

  Subsequently, the absolute angle detection ECU 54 outputs a neutral position signal to the steering reaction force ECU 60 and the front wheel steering ECU 70 in step S40. As a result, the steering reaction force ECU 60 and the front wheel turning ECU 70 recognize the neutral position based on the neutral position signal and perform zero point correction in the reaction force control and the turning angle control according to the steering angle.

On the other hand, if “NO” is determined in the step S38, the determination process of the step S41 is performed. In step S41, the relative angle difference θca is smaller than the relative angle difference cb (θca <θcb), or the relative angle difference θca is equal to the relative angle difference θcb and is not “0” (θca = θcb ≠ 0). Determine whether or not.
The determination in step S41 is to determine whether or not the steering position of the steering handle 11 is in the right steering region (or not).
If “YES” is determined in the step S41, the flag SIG indicating the steering region of the steering wheel 11 is set to “1” (S42). The flag SIG is set to “1” when the steering handle 11 is located in the right steering area, and is set to “0” when located in the left steering area.

In step S43, the steering angle magnitude | θ | is calculated based on the relative angle difference θca. The magnitude of the steering angle | θ | represents the rotation angle from the left steering limit position when the steering handle 11 is located in the left steering region, and from the neutral position when the steering handle 11 is located in the right steering region. Represents the rotation angle.
As shown in FIG. 8, the relative angle difference θca outputs a two-cycle periodic waveform signal in the process in which the steering wheel 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax. Therefore, two steering angles are obtained from the relative angle difference θca. In step S43, the steering angle magnitude | θ | is first calculated as a process of calculating the steering angle θ.

The magnitude of the steering angle | θ | can be calculated with reference to the steering angle | θ | table shown in FIG. The steering angle | θ | table is stored in the ROM of the absolute angle detection ECU 54, and the magnitude of the steering angle | θ | and the relative angle difference θca are associated with each other in a directly proportional relationship.
The steering angle magnitude | θ | may be calculated using a function. For example, if the rotation angle at which the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax is 2 · θmax, the relative angle difference θca is an electrical angle while the steering handle 11 rotates 2 · θmax. It changes by 4π. Therefore, the steering angle magnitude | θ | can be calculated as follows.
| Θ | = θmax · θca / (2 · π)

Subsequently, in step S44, the steering angle θ (absolute steering angle) of the steering handle 11 is calculated as follows.
θ = | θ |
In this case, since the steering handle 11 is located in the right steering region, the magnitude of the steering angle | θ | is set as the steering angle θ of the steering handle 11 as it is.

On the other hand, if “NO” is determined in the step S41, the steering wheel 11 is located in the left steering region, so the flag SIG is set to “0” in a step S45. Subsequently, in step S46, the magnitude of the steering angle | θ | is calculated based on the relative angle difference θca. This calculation process may be performed using the steering angle | θ | table or function shown in FIG. 11 as in step S43.
Next, in step S47, the steering angle θ (absolute steering angle) of the steering handle 11 is calculated as follows.
θ = | θ | −θmax
In this case, since the steering handle 11 is located in the left steering region, a value obtained by subtracting the left steering limit angle (−θmax) from the steering angle magnitude | θ | is set as the steering angle θ of the steering handle 11.

  When the absolute angle detection ECU 54 calculates the steering angle θ in steps S39, S44, and S47, in step S48, the steering angle detection signal indicating the steering angle θ (absolute steering angle θ) is transmitted to the steering reaction force ECU 60 and the front wheel drive. This is output to the rudder ECU 70 and this control routine is terminated.

This control routine is incorporated into the absolute steering angle calculation routine shown in FIG. 3 and repeatedly executed. Therefore, when the first resolver sensor 51, the second resolver sensor 52, and the third resolver sensor 53 are normal, the neutral position and the steering angle θ of the steering wheel 11 are determined based on the relative angle difference θca and the relative angle difference θcb. Calculated.
In calculating the steering angle θ, the left and right steering regions of the steering handle 11 are determined from the magnitude relationship between the relative angle difference θca and the relative angle difference θcb, and the magnitude of the steering angle | θ | is calculated from the relative angle difference θca. To do.

  The steering angle θ can be calculated using the relative angle difference θcb. However, in the present embodiment, the steering angle θ is calculated using the relative angle difference θca. This is because the detection accuracy of the steering angle θ is higher when the relative angle difference θca is used. As shown in FIG. 8, the relative angle difference θca has a larger amount of change with respect to the steering angle θ than the relative angle difference θcb. In this example, while the steering wheel 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax, the relative angle difference θcb changes by 2π in the electrical angle, whereas the relative angle difference θca has an electrical angle. Gives a change of 4π. Therefore, the detection accuracy is improved by using the relative angle difference θca.

The neutral position of the steering wheel 11 can be detected using the relative angle difference θcb, but in the present embodiment, it is calculated using the relative angle difference θca. This is because it is easier to detect the relative angle difference θca.
When the neutral position is detected using the relative angle difference θcb, it is only necessary to detect that the relative angle difference θcb is half of the value “2π” at the right steering limit angle + θmax, that is, “π”. However, since the relative angle difference θcb changes gently in proportion to the change in the steering angle θ, it is difficult to determine the neutral position.

  On the other hand, the value of the relative angle difference θca varies greatly at the neutral position. That is, when the steering handle 11 is rotated and passes through the neutral position, the relative angle difference θca is changed from “2π” to “0” (when steered in the right direction) or from “0” to “2π” ( Fluctuates significantly (when steering left). Therefore, the passage of the neutral position can be determined when a large change in the relative angle difference θca is detected. For example, the relative angle difference θca (n−1) detected immediately before is compared with the relative angle difference θca (n) detected this time, and the absolute value of the difference | θca (n−1) −θca (n) When | is equal to or greater than a predetermined value (for example, π), it can be determined that the neutral position has been passed. Therefore, compared with the case where the relative angle difference θcb is used, a large output fluctuation amount when the neutral position is passed can be obtained, and the neutral position can be easily detected.

  In the first absolute steering angle calculation routine, a relative angle difference θba (θb−θa) obtained by subtracting the relative angle θa from the relative angle θb may be used instead of the relative angle difference θcb. This is because the characteristic of the relative angle difference θba with respect to the steering angle θ is exactly the same as the characteristic of the relative angle difference θcb with respect to the steering angle θ, as shown in FIG.

Next, the second absolute steering angle calculation routine will be described.
The second absolute steering angle calculation routine is a control routine that is executed when an abnormality is detected only in the first resolver sensor 51, and is processed according to the flowchart shown in FIG.

  When the second abnormality routine is started, the absolute angle detection ECU 54 reads the output signals θb and θc of the second resolver sensor 52 and the third resolver sensor 53 in step S51. Subsequently, it is determined whether or not the relative angle θc is equal to or greater than the relative angle θb from the read signal (S52). If θc ≧ θb (S52: YES), the value obtained by subtracting θb from θc is set as a relative value. The angle difference is calculated as θcb (= θc−θb) (S53). On the other hand, if θc <θb (S52: NO), a value obtained by subtracting θb from θc and adding 2π is calculated as a relative angular difference θcb (= θc−θb + 2π) (S34).

As shown in FIG. 8, in the process of rotating the steering handle 11 from the left steering limit angle −θmax to the right steering limit angle + θmax, the second resolver sensor 52 outputs (n + 1) times of the sawtooth signal θb, The resolver sensor 53 outputs (n + 2) times of the sawtooth shape signal θc.
Therefore, the phase difference between the signal outputs of the resolver sensors 52 and 53 can be expressed by the relative angle difference θcb which is the difference between the relative angle θc and the relative angle θb, but the magnitude relationship between the two is reversed halfway. Therefore, when the magnitude relationship between the relative angle θc and the relative angle θb is reversed (θc <θb), 2π is added to the relative angle difference to obtain the relative angle difference θcb.

Subsequently, the steering angle θ is calculated based on the relative angle difference θcb calculated in step S53 or S54 (S55). The calculation of the steering angle θ is performed with reference to the steering angle θ table shown in FIG. This steering angle θ table is stored in the ROM of the absolute angle detection ECU 54, and correlates the steering angle θ of the steering handle 11 with the relative angle difference θcb.
The steering angle θ may be calculated using a function. For example, if the rotation angle at which the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax is 2 · θmax, the relative angle difference θcb is an electrical angle while the steering handle 11 rotates 2 · θmax. It changes by 2π. Therefore, the steering angle θ can be calculated as follows:
θ = θmax · θcb / π

  When the absolute angle detection ECU 54 calculates the steering angle θ in step S55, in the next step S56, a steering angle detection signal representing the steering angle θ (absolute steering angle θ) is sent to the steering reaction force ECU 60 and the front wheel steering. This is output to the ECU 70, and this control routine is terminated.

  The second absolute steering angle calculation routine is incorporated in the absolute steering angle calculation routine shown in FIG. 3 and is repeatedly executed when the first resolver sensor 51 is abnormal. Therefore, even when the first resolver sensor 51 fails, the steering angle θ is calculated based on the relative angle difference θcb between the second resolver sensor 52 and the third resolver sensor 53.

Next, a third absolute steering angle calculation routine will be described.
This third absolute steering angle calculation routine is a control routine that is executed when an abnormality is detected only in the third resolver sensor 53, and is processed according to the flowchart shown in FIG.

When the third abnormality routine is started, the absolute angle detection ECU 54 reads the output signals θa and θb of the first resolver sensor 51 and the second resolver sensor 52 in step S61. Subsequently, it is determined whether or not the relative angle θb is equal to or greater than the relative angle θa from the read signal (S62). If θb ≧ θa (S62: YES), the value obtained by subtracting θa from θb is used as a relative value. The angle difference is calculated as θba (= θb−θa) (S63). On the other hand, if θb <θa (S62: NO), a value obtained by subtracting θa from θb and adding 2π is calculated as a relative angular difference θba (= θb−θa + 2π) (S64).
As shown in FIG. 8, the relative angle difference θba calculated in this way is “0” in proportion to the increase in the steering angle θ when the steering wheel 11 is rotated from the left steering limit angle −θmax to the right steering limit angle + θmax. ”To“ 2π ”linearly.

Subsequently, the steering angle θ is calculated based on the relative angle difference θba calculated in step S63 or S64 (S65). The calculation of the steering angle θ is performed with reference to the steering angle θ table shown in FIG. This steering angle θ table is stored in the ROM of the absolute angle detection ECU, and associates the steering angle θ of the steering wheel 11 with the relative angle difference θba.
The steering angle θ may be calculated using a function. For example, if the rotation angle at which the steering handle 11 rotates from the left steering limit angle −θmax to the right steering limit angle + θmax is 2 · θmax, the relative angle difference θba is an electrical angle while the steering handle 11 rotates 2 · θmax. It changes by 2π. Therefore, the steering angle θ can be calculated as follows:
θ = θmax · θba / π

  When the absolute angle detection ECU 54 calculates the steering angle θ in step S65, in the next step S66, a steering angle detection signal representing the steering angle θ (absolute steering angle θ) is sent to the steering reaction force ECU 60 and the front wheel steering. This is output to the ECU 70, and this control routine is terminated.

  The third absolute steering angle calculation routine is incorporated in the absolute steering angle calculation routine shown in FIG. 3 and is repeatedly executed when the third resolver sensor 53 is abnormal. Therefore, even when the third resolver sensor 53 fails, the steering angle θ is calculated based on the relative angle difference θba between the first resolver sensor 51 and the second resolver sensor 52.

Next, a fourth absolute steering angle calculation routine will be described.
This fourth absolute steering angle calculation routine is a control routine that is executed when an abnormality is detected only in the second resolver sensor 52, and is processed according to the flowchart shown in FIG.

  When the fourth abnormality routine is started, the absolute angle detection ECU 54 reads the output signals θa and θc of the first resolver sensor 51 and the third resolver sensor 53 in step S71. Subsequently, it is determined whether or not the relative angle θc is equal to or larger than the relative angle θa from the read signal (S72). If θc ≧ θa (S72: YES), the value obtained by subtracting θa from θc is set as a relative value. The angle difference is calculated as θca (= θc−θa) (S73). On the other hand, if θc <θa (S72: NO), a value obtained by subtracting θa from θc and adding 2π is calculated as a relative angular difference θca (= θc−θa + 2π) (S74).

Subsequently, the absolute angle detection ECU 54 calculates the steering angle magnitude | θ | based on the relative angle difference θca calculated in step S73 or S74 (S75).
The magnitude of the steering angle | θ | represents a rotation angle from the left steering limit position −θmax when the steering handle 11 is located in the left steering region, and is a neutral position when the steering handle 11 is located in the right steering region. Represents the rotation angle from.
The calculation of the steering angle magnitude | θ | is similar to steps S43 and S46 in the first absolute steering angle calculation routine of FIG. 4, with reference to the steering angle | θ | table shown in FIG. Calculate using.

  Subsequently, in step S76, the absolute angle detection ECU 54 determines whether or not the value of the relative angle difference θca has changed from “2π” to “0”. That is, as shown in FIG. 8, the value of the relative angle difference θca is a sawtooth-shaped periodic wave signal with respect to the steering angle θ, but from the value “2π” that becomes the waveform apex to the value “0 that becomes the waveform valley. It is determined whether or not it has changed to “”. For example, in the signal waveform of the relative angle difference θca in FIG. 8, the point A is the waveform vertex and the point B is the waveform valley. In this case, the passage of the waveform apex A is determined from the relationship between the relative angle difference θca (n−1) detected immediately before and the relative angle difference θca (n) detected this time.

When the steering handle 11 located in the left steering region rotates rightward and enters the right steering region, the relative angle difference θca passes through the waveform vertex A as indicated by an arrow a1 in FIG. Decrease by 2π. Therefore, in the present embodiment, for example, the value of the relative angular difference θca (n) detected this time has decreased by a predetermined value (for example, π) or more with respect to the relative angular difference θca (n−1) detected immediately before. In this case, it is determined that the value of the relative angle difference θca has changed from “2π” to “0”.
In this case, it is determined that the steering handle 11 has entered the right steering area from the left steering area, and the flag SIG is set to “1”.

  On the other hand, if it is determined in step S76 that the value of the relative angle difference θca has not changed from “2π” to “0” (S76: NO), then the determination process of step S78 is performed. In step S78, it is determined whether or not the value of the relative angle difference θca has changed from “0” to “2π”. That is, it is determined whether or not the sawtooth-shaped output signal representing the value of the relative angle difference θca has changed from the value “0” corresponding to the waveform valley B to the value “2π” corresponding to the waveform vertex A.

Even in this case, the passage of the waveform apex A is determined from the relationship between the relative angle difference θca (n−1) detected immediately before and the relative angle difference θca (n) detected this time.
When the steering handle 11 located in the right steering region rotates leftward and enters the left steering region, the relative angle difference θca passes through the waveform valley B as shown by an arrow a2 in FIG. Sometimes increases by 2π. Therefore, in the present embodiment, for example, the value of the relative angle difference θca (n) detected this time has increased by a predetermined value (for example, π) or more with respect to the relative angle difference θca (n−1) detected immediately before. In this case, it is determined that the value of the relative angle difference θca has changed from “0” to “2π”.
In this case, it is determined that the steering handle 11 has entered the left steering area from the right steering area, and the flag SIG is set to “0”.
If the determinations in steps S76 and S78 are “NO”, the flag SIG setting process is not performed.

Next, the absolute angle detection ECU 54 advances the process to step S80. In this step S80, it is determined whether or not the flag SIG is set to “1”. If the flag SIG = 1 (S80: YES), the steering angle θ (absolute steering angle) of the steering handle 11 is calculated as follows in step S81.
θ = | θ |
In this case, since the steering handle 11 is located in the right steering region, the magnitude of the steering angle | θ | is set as the steering angle θ of the steering handle 11 as it is.

On the other hand, if “NO” is determined in the step S80, that is, if the flag SIG = 0, the steering handle 11 is located in the left steering region, and therefore the steering angle θ (absolute) of the steering handle 11 is determined in the step S82. (Steering angle) is calculated as follows:
θ = | θ | −θmax
In this case, since the steering handle 11 is located in the left steering region, a value obtained by subtracting the left steering limit angle (−θmax) from the steering angle magnitude | θ | is set as the steering angle θ of the steering handle 11.

  When the absolute angle detection ECU 54 calculates the steering angle θ in step S81 or step S82, in step S83, the steering angle detection signal indicating the steering angle θ (absolute steering angle θ) is transmitted to the steering reaction force ECU 60 and the front. This is output to the wheel steering ECU 70, and this control routine is terminated.

  The fourth absolute steering angle calculation routine is incorporated in the absolute steering angle calculation routine shown in FIG. 3 and is repeatedly executed when the second resolver sensor 52 is abnormal. Therefore, even when the second resolver sensor 52 fails, the steering angle θ is calculated based on the relative angle difference θca between the first resolver sensor 51 and the third resolver sensor 53.

  In the fourth absolute steering angle calculation routine, when a change in the relative angle difference θca (“2π” to “0” or “0” to “2π”) is detected in step S76 or step S78. The neutral position signal may be output to the steering reaction force ECU 60 and the front wheel steering ECU 70.

As described above, according to the vehicle steering apparatus of the present embodiment, the steering angle θ and the neutral position are calculated based on the relative angle differences θba, θcb, θca from the output signals of the three resolver sensors 51, 52, 53. Easy to calculate. In addition, since the steering angle θ is calculated using the relative angle difference θca having a large fluctuation amount with respect to the change in the steering amount, the steering angle detection accuracy is extremely high.
Further, when detecting the neutral position of the steering wheel 11, the detection is easy because it is based on the value of the relative angle difference θca (θca = 0). That is, when the steering position of the steering wheel 11 passes through the neutral position, the relative angle difference θca varies greatly from “0” to “2π” or from “2π” to “0”. Accordingly, when a large change in the relative angle difference θca is detected, it is determined that the steering handle 11 is in the neutral position (steering angle θ = 0), and thus the detection is easy and the detection accuracy is high.

  Since the absolute steering angle θ and the neutral position are always calculated when the vehicle is in a driving state, there is no need to store it until the next driving after the driving is stopped. Therefore, it is not necessary to provide a new configuration assuming that the power battery is removed, and the configuration can be implemented at low cost. Further, the consumption of dark current in the storage device can be reduced. Furthermore, unlike the conventional apparatus, it is not necessary to store the neutral position in the manufacturing process, so that the number of manufacturing steps can be reduced.

Furthermore, even if one of the resolver sensors fails during vehicle operation, the steering angle θ is calculated by the other resolver sensors, so that the steering reaction force control by the steering reaction force ECU 60 and the front wheel rotation by the front wheel turning ECU 70 are performed. Rudder control can be continued.
In addition, since the first to fourth absolute steering angle calculation processes are stored as a control program and the process is selected according to the failure state of the resolver sensor, the optimum absolute steering angle calculation process suitable for the failure state can be performed. .
Further, when even one resolver sensor has failed since the start of the vehicle, the steering input shaft 12 and the steering output shaft 24 are connected by the operation of the electromagnetic clutches 32 and 33, so that the steering handle 11 is rotated. The left and right front wheels FW1, FW2 can be directly steered by operation.
As a result, the reliability of the steer-by-wire steering device can be improved, and the safety of the vehicle can be improved.

  The steering device has been described as an embodiment of the rotation angle detection device of the present invention. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention. .

The relative angle difference θba and the relative angle difference θcb in the present embodiment correspond to the first electrical angle of the present invention, and the relative angle difference θca in the present embodiment corresponds to the second electrical angle of the present invention. In addition, the processing of steps S33, S34, S53, S54, S63, and S64 in the absolute steering angle calculation routine performed by the absolute angle detection ECU 54 in the present embodiment corresponds to the first electrical angle calculation means of the present invention. The processes of steps S36, S37, S73, and S74 in the absolute steering angle calculation routine performed by the absolute angle detection ECU 54 correspond to the second electrical angle calculation means of the present invention. Further, the processing in steps S38 to S47 in the absolute steering angle calculation routine performed by the absolute angle detection ECU 54 in the present embodiment corresponds to the absolute steering angle calculation means of the present invention.
Further, the processing of steps S21, S23, S25, and S27 in the absolute steering angle calculation routine performed by the absolute angle detection ECU 54 in the present embodiment corresponds to the abnormality detection means of the present invention. Further, the processing of steps S55, S65, and S75 to S82 in the steering angle calculation routine performed by the absolute angle detection ECU 54 in the present embodiment corresponds to the abnormal absolute steering angle calculation means of the present invention.

1 is an overall schematic diagram of a steering apparatus for a vehicle including a steering angle detection device as one embodiment of the present invention. It is a flowchart showing an initial control routine. It is a flowchart showing an absolute steering angle calculation routine. It is a flowchart showing a 1st absolute steering angle calculation routine. It is a flowchart showing a 2nd absolute steering angle calculation routine. It is a flowchart showing a 3rd absolute steering angle calculation routine. It is a flowchart showing the 4th absolute steering angle calculation routine. It is explanatory drawing showing a relative angle, an absolute steering angle, and a relative angle difference. It is explanatory drawing showing the steering reaction force table for calculating a target steering reaction force from a steering angle. It is explanatory drawing showing the turning angle table for calculating a target front-wheel turning angle from a steering angle. FIG. 6 is an explanatory diagram showing a steering angle | θ | table for calculating a steering angle magnitude | θ | from a relative angle difference; It is explanatory drawing showing the steering angle (theta) table for calculating steering angle (theta) from a relative angle difference.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Steering operation device, 11 ... Steering handle, 12 ... Steering input shaft, 13 ... Electric motor for steering reaction force, 20 ... Steering device, 22 ... Electric motor for steering, 24 ... Steering output shaft, 40 ... Electricity Control device, 50 ... steering angle detection device, 51 ... first resolver sensor, 51s ... first resolver, 51c ... first relative angle detection circuit, 52 ... second resolver sensor, 52s ... second resolver, 52c ... second relative Angle detection circuit, 53 ... third resolver sensor, 53s ... third resolver, 53c ... third relative angle detection circuit, 54 ... absolute angle detection ECU, θ ... steering angle (absolute steering angle), θa, θb, θc ... Relative angle, θba, θcb, θca... Relative angle difference.

Claims (5)

A first resolver sensor that outputs n periodic waveform signals when the steering member is steered from the left steering limit position to the right steering limit position;
A second resolver sensor that outputs a (n + 1) number of periodic waveform signals when the steering member is steered from the left steering limit position to the right steering limit position;
A third resolver sensor that outputs a periodic waveform signal of (n + 2) times when the steering member is steered from the left steering limit position to the right steering limit position;
Based on the difference between the signal output value of the first resolver sensor and the signal output value of the second resolver sensor, or the difference between the signal output value of the second resolver sensor and the signal output value of the third resolver sensor. A first electrical angle calculating means for calculating a first electrical angle having a characteristic in which one peak value appears with respect to a change in the steering angle in a steerable range from the left steering limit position to the right steering limit position;
Based on the difference between the signal output value of the first resolver sensor and the signal output value of the third resolver sensor, 2 for the change of the steering angle in the steerable range from the left steering limit position to the right steering limit position. Second electrical angle calculating means for calculating a second electrical angle having a characteristic in which two peak values appear;
Based on the first electrical angle calculated by the first electrical angle calculation means and the second electrical angle calculated by the second electrical angle calculation means, the neutral position and the absolute steering angle of the steering member are calculated. A steering angle detection device comprising: an absolute steering angle calculation means.   The absolute steering angle calculation means determines that the steering member is in a neutral position when the value of the first electrical angle is not zero and the value of the second electrical angle is zero. The steering angle detection device according to claim 1.   The absolute steering angle calculating means determines whether the steering position of the steering member is in the right steering area or the left steering area based on the magnitude relationship between the first electrical angle and the second electrical angle, 3. The steering angle detection device according to claim 1, wherein the absolute steering angle is calculated based on a region determination result and a value of the second electrical angle. An abnormality detecting means for detecting an abnormality of the first resolver sensor, the second resolver sensor, and the third resolver sensor;
An abnormality that calculates an absolute steering angle of the steering member based on a difference between signal output values of two resolver sensors in which no abnormality is detected when an abnormality of one of the three resolver sensors is detected The steering angle detection device according to any one of claims 1 to 3, further comprising: hour absolute steering angle calculation means. When the abnormality is detected in the second resolver sensor, the absolute steering angle calculation means at the time of abnormality determines the steering position of the steering member based on the transition of the second electric angle calculated by the second electric angle calculation means. 5. The steering according to claim 4, wherein it is determined whether the vehicle is in a right steering region or a left steering region, and the absolute steering angle is calculated based on the region determination result and the value of the second electrical angle. Angle detection device.

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