JPH02256562A - Judgement of steering state of all electrical type power steering device - Google Patents

Abstract

PURPOSE:To obviate the need of a steering angle sensor by searching the between-motor terminal voltage value in the steering holding state from the indication value of the motor electric current and judging the steering state from the difference between the actual between-motor terminal voltage value. CONSTITUTION:The indication value and direction of the motor electric current are calculated in a CPU 4 from the handle torque detected by a torque sensor 1 and the car speed detected by a car speed sensor 3, and a motor 18 is controlled according to the results of the calculation. When the motor 18 is in revolution, the between-terminal voltage VM of the motor is detected, and the between-terminal voltage VMSET of the motor in the steering holding state for the above-described indication value of the motor is calculated. The both voltage values VM and VMSET are compared, and if VM>VMSET, and the value VM-VMSET is larger than V, the cut-in state is judged, and if the value VM-VMSET is smaller than V, the steering holding state is judged. Further, when VM<VMSET, and the value VMSET-VM is larger than V, the return state is judged, and if the value VMSET-VM is smaller, the steering holding state is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for determining a steering state in an all-electric power steering system.

[Conventional technology]

The conventional steering state determination method detects the torque and steering angle for each unit time, and determines whether the steering is held or not when the torque change and steering angle change per unit time are within the permissible predetermined values. At one point, it was determined that the steering wheel was turning or returning.

The method for determining the above-mentioned rudder holding state is, for example, disclosed in Japanese Patent Application Laid-Open No. 63-1805.
It is described in Publication No. 66. Further, the method for determining the cutting state and return state is described in, for example, Japanese Utility Model Publication No. 51-38101.

[Problem to be solved by the invention]

As mentioned above, in the conventional steering state determination method,
It is necessary to detect torque and steering angle, and the two
There is a problem in that two sensors must be provided, and the device for determining the steering condition becomes expensive.

The present invention has been made in view of these points, and its purpose is to eliminate the need for using a steering angle sensor (
The object of the present invention is to provide a method that can determine the steering state.

[Means to solve the problem]

In order to achieve such an object, the present invention searches for the voltage value between the motor terminals in the steering-holding state from the motor current instruction value, and calculates the difference between the actually detected voltage value between the motor terminals and the retrieved voltage value between the motor terminals. The difference is calculated and the steering state is determined based on this difference.

[Effect]

In the steering state determination method according to the present invention, if the difference between the retrieved motor terminal voltage value and the detected motor terminal voltage value is within a predetermined tolerance, the steering is held, and if it is outside the predetermined tolerance, the steering is turned or returned. It is judged that the condition.

〔Example〕

FIG. 5 is a circuit diagram showing an assist motor drive control circuit for explaining an embodiment of the method for determining the steering state of an all-electric power steering apparatus according to the present invention. In the same figure, 1
is a torque sensor that outputs a torque signal a, 2 is a filter for removing noise from the torque signal a, 3 is a vehicle speed sensor that outputs a vehicle speed signal, and 4 is a CP that controls the entire circuit.
U, 4a is an A/D converter of the CPU 4, 5 is a D/A converter connected to the output side of the CPU 4, 6 is a comparator, 78 is an AND circuit, 9 to 12 are drive units, 13 is a relay, etc. Power switch means, 14 to 17 are transistors connected to drive units 9 to 12, 18 is an assist motor, 19.20
21 is a resistor for motor current detection, 21 is a current detector, and 22.
23 is an analog switch, 24 is a buffer, and BT is a battery.

Next, the general operation of the circuit shown in FIG. 5 will be explained. The torque signal a is input to the A/D converter 4a of the CPU 4,
The vehicle speed signal is directly input to the CPU 4. CPU4 is
Drive current value c t-D as command value from signals a and b
/ Outputs to the A converter 5 and also outputs a right signal d and a left signal e that determine the rotation direction of the motor. The analog drive current value output from the D/A converter 5 is compared with the motor current value from the current detector 21 by a comparator 6, and if the drive current value is larger than the motor current value, an AND circuit 7.8
``1'' is output for the value, and ``0'' is output if the value is smaller.

Here, assuming that the CPU 4 is outputting the right signal d of "1" and the left signal e of rOJ, if the drive current value is larger than the motor current value, the AND circuit 7 outputs the signal rlJ. Then, the driving section 9 drives the transistor 14. Further, the drive unit 12 directly inputs the right signal d from the CPU 4 and drives the transistor 17. Therefore, motor 18
A current flows from left to right, and the motor 18 rotates in the right direction. If the drive current value is smaller than the motor current value, or if the right signal d and left signal e are both "0",
Neither transistor is driven.

Note that in the case of clockwise rotation, the analog switch 22 is turned on, and the voltage at the left end of the motor 18 is input to the CPLJ 4 via the buffer 24. At this time, the voltage at the right end of the motor 18 is approximately close to the body potential of the vehicle body, and therefore the voltage at the right end of the motor 18 is close to the body potential of the vehicle body.
The voltage at the left end of is approximately the voltage between the motor terminals. In the case of counterclockwise rotation, the analog switch 23 is turned on and the same operation is performed.

Next, one embodiment of the present invention will be described using FIG. 1, FIG. 2, FIG. 5, and FIG. 6. When the ignition key switch is turned on, power is supplied to the assist motor drive control circuit shown in Fig. 5, and the memory in the CPU 4 is cleared.
An initial diagnosis is made to see if there is any abnormality in the motor (steps 31 and 32).Next, the torque sensor 1 detects the steering wheel torque, and a motor current instruction value is calculated from this steering wheel torque and vehicle speed (step 33). .34).

A method for calculating this motor current instruction value will be described.

The direction of the torque is determined from the voltage value of the torque signal a shown in FIG. This is because the CP'U4 has a map with torque on the horizontal axis and voltage on the vertical axis as shown in FIG. 6(a), so the direction can be determined using this map.

Next, the torque value T is calculated using a symmetrical torque calculation map as shown in Fig. 6(C), and the vehicle speed value S is calculated based on the vehicle speed signal. The instruction value is calculated using a map (instruction value map) of instruction value (drive current value) versus torque using vehicle speed value S as a parameter.

In this way, the motor current instruction value and its direction 2 are calculated. Then, these values are output to the motor 18 (
step 35), which causes current to flow to the motor 18;
The motor 18 starts rotating, and the voltage vH between the motor terminals at this time is detected to determine the steering state (step 3).
6). This is repeated thereafter (steps 33 to 36).

The above method for determining the steering state will be explained using the flowchart for determining the steering state shown in FIG.

First, the motor terminal voltage VM is detected (step 37
). Next, the motor terminal voltage v0° in the steering-holding state is determined (step 38) with respect to the motor current instruction value determined in FIG. 1 (step 34), and this vo, 7 is calculated as shown in FIG.
It is obtained from the motor terminal voltage versus motor current characteristic of n=0 shown in FIG. Figure 6 (in dl, n is the parameter of motor rotation speed, n = n 1 + n 2
*The characteristic line of n3 shows the characteristics when the drive current for clockwise rotation flows and the motor rotates clockwise, n=-nl, -N2.
The characteristic line -N3 shows the characteristics when the drive current for counterclockwise rotation flows and the motor rotates counterclockwise.

Next, compare the voltages VM and vxsty, and find that V is vms
.

If it is larger, calculate the value of VW-V
If it is larger than V, it is determined that the cutting state is present (step 41), and if the value of V,4Vnsty is smaller than ΔV, it is determined that the steering state is maintained (step 42), =, Δ■
is the value shown in Fig. 6(d), and the offset,
This is a predetermined tolerance value to prevent malfunctions due to noise or the like. In step 39, V is vo. vN if smaller. −■ Find the value of 8 (step 43),
If the VMstt VM(7) value is greater than ΔV, it is determined that the return state is reached (step 44), and V and NET-
If the VHO value is smaller than ΔV, it is determined that the steering is held (step 42).

In this manner, in the embodiments shown in FIGS. 1 and 2, the steering condition can be determined based on the voltage between the motor terminals and the steering wheel torque, and there is no need for a steering angle sensor, which was required in the past.

Next, other embodiments of the present invention will be described using FIGS. 3, 4, 5, and 6. In FIG. 3, when the ignition key switch is turned on, power is supplied to the assist motor drive control circuit shown in FIG.
The memory in the motor is cleared and an initial diagnosis is made to see if there is any abnormality in the motor (steps 51 and 52).Next, the voltage value of the torque signal a is detected (step 53), and the torque is calculated from this voltage value. The direction is determined (step 54).

This is because the CPU 4 has a map with torque on the horizontal axis and voltage on the vertical axis as shown in Figure 6(a), so the direction can be determined using this map, as shown in Figure 6(h). Using such a symmetrical torque calculation map, the torque value T° is calculated (step 55), and this value is stored in the memory of the CPU 4. Also, calculate the vehicle speed value 3 based on the vehicle speed signal (
Step 56).

Next, a change in torque ΔT=ITI-T21 is calculated from the previous torque value T2 and the current torque value T1 (step 57). Next, the command value is calculated using a map of the command value (drive current value) versus torque using the vehicle speed value S as a parameter as shown in FIG. The CPU 4 outputs the signal along with the right signal d or the left signal e (step 59), thereby supplying current to the motor 18 and causing the motor to start rotating. In such a state, the steering state is determined (step 60), and this is repeated thereafter (step 5).
3-60).

The method for determining the above-mentioned steering state will be explained using FIG. 4. First, the voltage V between the motor terminals. (Step 61) Next, the voltage VHS between the motor terminals in the holding state with respect to the motor current instruction value obtained in Fig. 3 (Step 58) is detected.
Find a (step 62) -ko(D vxst
yC, Fig. 6(d) shows t The voltage vH and VH2A, which are obtained from the nxQ characteristic of the voltage between the motor terminals and the motor current, are compared, and if vH is larger than Vtts□, Find the value of V M V N11l (steps 63 and 64), VW-V engineering 37. If the value of is larger than ΔV, the current torque T1 and the previous torque T2 are compared (step 64.65), and if TI>72, it is determined that there is a cutting state (step 66), and TI≦
In case of T2, judge, do not judge as undecidable, V, 4-
V. , in the case of t7≦ΔV, the absolute value of Tl-72 lTl
−721 and ΔT are compared (step 67), lT
If ITI-721<ΔT, it is determined that the steering is held (step 6B), and if ITI-T21≧ΔT, it is determined that the determination is not possible and the determination is not made. As mentioned above, ΔV is shown in Figure 6 (
The value is as shown in d).

If vH is smaller than v, , □ in step 63, the value of VWS□-vll is determined (step 69).

Vtts. If the value of -vH is larger than Δ■, the current torque T1 and the previous torque T2 are compared (step 69.To), and if TI<72, it is determined that the state is in the return state (step 71). If T1≧T2, it is determined that the determination is not possible and the determination is not made, and the process proceeds to step 69.
When VH≦ΔV, ITl-T21 and ΔT are compared (step 67), and when ITI-T21<ΔT, it is determined that the steering is held (step 68). ITI-T
In the case of 21≧ΔT, it is determined that the determination is impossible and the determination is not made.

In this manner, in the embodiments shown in FIGS. 3 and 4, the steering condition can be determined based on the voltage between the motor terminals and the steering wheel torque, and there is no need for a steering angle sensor, which was required in the past. In addition, not only the voltage between the motor terminals v8, but also the torque T, 1
Since the previous torque T2 is also determined, the steering state can be determined more reliably.

〔Effect of the invention〕

As explained above, the present invention searches for the motor terminal voltage value in the steering-holding state from the motor current instruction value, calculates the difference between the actually detected motor terminal voltage value and the retrieved motor terminal voltage value, and calculates the difference between the motor terminal voltage value actually detected and the motor terminal voltage value found. Determining the steering state based on the difference eliminates the need for a conventionally required steering angle sensor, which has the effect of making the device for determining steering inexpensive. Furthermore, an increase in the number of connector terminals due to the addition of the steering angle sensor can be prevented, and an increase in installation space can also be prevented.

[Brief explanation of drawings]

1, 2, 3, and 4 are flowcharts for explaining two embodiments of the method for determining the steering state of an all-electric power steering device according to the present invention, and FIG. The control circuit diagram, FIG. 6, is a graph showing various maps stored in the memory within the CPU.

Claims (1)

[Claims] In a method for determining the steering state of an all-electric power steering device in which steering force is assisted by a motor, the voltage value between the motor terminals in the steering holding state is searched from the motor current instruction value, and the voltage value between the motor terminals actually detected and the search are performed. A method for determining a steering state of an all-electric power steering system, characterized in that the difference between the voltage value and the motor terminal voltage value determined is determined, and the steering state is determined based on this difference.