Source: https://insight.rpxcorp.com/pat/US5247466A
Timestamp: 2019-10-18 22:16:04
Document Index: 280556216

Matched Legal Cases: ['art 5', 'art 44', 'art 45', 'art 45', 'art 44', 'art 44']

Patent US 5,247,466 A
Angular rate detection apparatus, acceleration detection apparatus and movement control apparatus, of moving body
US 5,247,466 A
Filed: 03/25/1991
1. An apparatus for detecting an angular rate of a moving body, comprising:
first and second acceleration sensors each having a detection direction;
means for mounting said first and second acceleration sensors on said moving body so that said first and second acceleration sensors have substantially the same detection direction on a plane and a fixed distance therebetween in the detection direction; and
means for detecting an angular rate of the moving body around an axis perpendicular to the plane on which said first and second acceleration sensors are disposed, on the basis of outputs of and a positional relation between said first and second acceleration sensors.
An apparatus for detecting an angular rate of a moving body has first and second sensors each of which has a detection direction, the first and second acceleration sensors are mounted at fixed locations on a moving body so that the first and second acceleration sensors have substantially the same detection direction on a plane and a fixed distance therebetween in the detection direction, and the angular rate (.omega.) of the moving body is detected according to the following equation: ##EQU1## wherein .DELTA.G is an acceleration difference and R is the distance between the first and second acceleration sensors in the detection direction.
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2. The apparatus according to claim 1, wherein said means for detecting angular rate calculates the angular rate (.epsilon.) of said moving body according to the following equation:
##EQU8## wherein .DELTA.G is a difference between acceleration detected by said first acceleration sensor and acceleration detected by said second acceleration sensor, and R, said distance between said first and second acceleration sensors in the detection direction.
5. An apparatus for detecting an angular rate of an automobile, comprising:
means for mounting said first and second acceleration sensors on a car body of said automobile so as to position on a plane substantially parallel to floor of said automobile, said detection direction being substantially the same as each other and said first acceleration sensor being separated from said second acceleration sensor to provide a distance (R) therebetween with respect to the detection direction;
means for detecting an angular rate (e) of movement of said automobile around an axis perpendicular to said plane on the basis of a difference (.DELTA.G) between outputs from said first and second sensors and the distance (R) along the following relation;
6. The apparatus according to claim 5, wherein said first and second acceleration sensors are mounted front and rear portions of said automobile, respectively.
12. An apparatus detecting a physical quantity of movement of a moving body which includes parallel movement on a plane and a rotational movement around an axis perpendicular to the plane, said apparatus comprising;
means for mounting said first and second acceleration sensors on said moving body so as to be positioned in said plane with a fixed distance (R) between said first and second acceleration sensors in the detection direction; and
means for calculating physical quantity representative of one of an angular rate of said rotational movement and acceleration of said parallel movement of said moving body, on the basis of a difference between outputs from said first and second acceleration sensors and said distance (R) between said first and second acceleration sensors with respect to the detection direction.
13. The apparatus according to claim 12, wherein said means detecting a physical quantity includes filtering means for filtering the outputs from said first and second acceleration sensors.
15. A control apparatus for controlling movement of a moving body, comprising;
first and second acceleration sensors each having a detection direction and outputting an output corresponding to detected acceleration;
means for fixing said first and second acceleration sensors on said moving body so as to position in a plane of said moving body with a distance (R) between said first and second acceleration sensors in the detection direction;
means for detecting an angular rate (.epsilon.) of said moving body around an axis perpendicular to said plane of said moving body according to an equation .epsilon.=.sqroot..DELTA.G/R, wherein .DELTA.G is a difference between the outputs from said first and second acceleration sensors;
a comparator for comparing a target angular rate of said moving body and the detected angular rate to produce a difference;
means for generating a control input corresponding to said difference between said target angular rate and said detected angular rate; and
an actuator mounted on said moving body for actuating a control element in response to the control input so that an angular rate of said moving body approaches to the target value.
According to an aspect of the present invention, the means for detecting angular rate detects an angular rate (.omega.) of the moving body according to the following equation: ##EQU2## wherein .DELTA.G is an acceleration difference and R is the distance between the first and second acceleration sensors in the detection direction.
An apparatus for detecting angular rate of the moving body 1 comprises first and second acceleration sensors 2, 3 which have detection directions (I), (II), respectively. The first and second acceleration sensors 2, 3 are fixed to the moving body 1 at setting points A and B, respectively. Assuming that the center of gravity 4 of the moving body 1 is the center of the rotation of the moving body 1, the setting point A of the first acceleration sensor 2 is positioned at a radius R.sub.a at a right side of the gravity center 4 and the setting point B of the second acceleration sensor 3 is positioned at a radius R.sub.b at a left side. The setting points A, B have angles .theta.a, .theta.b with respect to the x-axis. The detection directions (I), (II) of the acceleration sensors 2, 3 each are parallel to the x-axis.
Acceleration of the moving body 1 detected by the acceleration sensors 2, 3 is an x-component of acceleration of parallel movement of the moving body 1 and an x-component of an acceleration due to a centrifugal force caused by rotational movement of the moving body 1. Accordingly, the accelerations G.sub.sa, G.sub.sb detected by the first and second acceleration sensors 2, 3 are expressed by the following equations, respectively:
G.sub.sa =G.sub.la +G.sub.ya cos .theta.a (1)
G.sub.sb =G.sub.lb +G.sub.yb cos .theta.b (2)
G.sub.la is acceleration of parallel movement at the A point,
G.sub.lb is acceleration of parallel movement at the B point,
G.sub.ya is acceleration due to rotational movement (centrifugal force) at the A point,
G.sub.yb is acceleration due to rotational movement (centrifugal force) at the B point,
G.sub.sa is acceleration at the point A, really detected by the sensor 2, and
G.sub.sb is acceleration at the point B, really detected by the sensor 3.
Here, as for the parallel movement acceleration G.sub.la, G.sub.lb, the following relation is established;
G.sub.la =G.sub.lb (3)
A difference .DELTA.G between detection acceleration G.sub.sa, G.sub.sb at the points A, B is given as follows, employing the equations (1), (2) and (3) ##EQU3##
When the moving body rotates, centrifugal force takes place. The centrifugal force is expressed by (mass).times.(radius).times.(angular rate).sup.2, and acceleration due to the rotation is (radius).times.(angular rate).sup.2, therefore, acceleration due to the rotation at the points A, B are expressed as follows, respectively:
G.sub.ya =R.sub.a .multidot..omega..sup.2 (5)
G.sub.yb =R.sub.b .multidot..omega..sup.2 (6)
.DELTA.G=.omega..sup.2 (R.sub.a cos .theta.a-R.sub.b cos .theta.b)(7)
Both sides of the equation (7) are plus. From the equation (7), an angular rate .omega. is given as follows: ##EQU4##
R=R.sub.a cos .theta.a-R.sub.b cos .theta.b (9)
In the equation (8) or (10), R.sub.a, R.sub.b, .theta.a and .theta.b are fixed values, therefore, R also is a fixed value representing a positional relation of the first and second acceleration sensors mounted on the moving body 1. On the other hand, .DELTA.G is a difference between the detection acceleration by the first and second acceleration sensors, so that it is found that the angular rate .omega. can be calculated according to the equation (8) or (10), based on the positioned relation and the detection acceleration.
The apparatus for detecting angular rate further comprises means for mounting the first and second acceleration sensors 2, 3 on the moving body 1 at a distance R therebetween as mentioned above so as to have the same detection direction, and a processing circuit for detecting the angular rate from the acceleration difference .DELTA.G and the positional relation R according to the equation (8) or (10).
As for the positional relation between the first and second acceleration sensors 2, 3, the equation (9) should not be zero. If this condition is satisfied, any values of .theta.a, .theta.b, R.sub.a, R.sub.b can be used. However, as for .theta.a, .theta.b, it is desirable to be .theta.a=0.degree. and .theta.b=180.degree. , namely, the first and second acceleration sensors 2, 3 are positioned on a line, which positional relation makes the distance R larger. When .theta.b is closed to .theta.a, for example, .DELTA.G is small, so that discrimination of .DELTA.G is less. However, in such a case also, an angular rate can be detected.
As for R.sub.a and R.sub.b, when .theta.a.noteq..theta.b, the angular rate can be detected even if R.sub.a =R.sub.b.
In FIG. 4, detection acceleration G.sub.sa, G.sub.sb also is acceleration G.sub.sa, G.sub.sb has a small variation component therein, the small variation component of the acceleration influences the angular rate to produce variation components in the angular rate. If it is desired to remove these variation components, it can be achieved by a filter such as a low-pass filter. Further, when attention is given to a part 5 of the acceleration data in FIG. 4, it is found that acceleration in parallel movement is changed rapidly. However, the difference .DELTA.G between G.sub.sa and G.sub.sb is not changed rapidly at a time of the rapid change of the angular rate.
Filtering by the signal processing circuit 10, 11, 12 is effected to remove small variations appearing in G.sub.sa, G.sub.sb, as shown in FIG. 4. Namely, low-pass filtering is effected. In an analogue type filter, the CR time constant is changed. In an example described later, the resistance R is changed.
In FIG. 6, a characteristic of output voltage and acceleration to be detected (g) in each acceleration sensor is illustrated. The characteristic is linear as expressed by a straight line. The acceleration sensor 2, 3 has a construction wherein, when acceleration g is 0, the sensor outputs a certain output voltage V.sub.2. The sensor has polarity because the acceleration has a direction. The output voltage of the sensor is V.sub.1 at the upper limit of the acceleration g and V.sub.3 at the lower limit.
Output voltage V.sub.1, V.sub.2, V.sub.3 of each acceleration sensor 2, 3 is in a range from several millivolts mV to several volts V. In case of the output of several volts V, it is not necessary to amplify it to a large extent, however, in case of several millivolt mV, it is desirable to amplify the output to a large extent. In particular, it is necessary for the signal processing circuit 12 to have an amplification function. The circuit 12 makes an acceleration difference .DELTA.G from outputs of the acceleration sensor 2, 3. The acceleration difference is small. An example of the acceleration difference is shown in FIG. 7 in which yaw rate conditions also are shown. It is noted from FIG. 7 that .DELTA.G.sub.2 and .DELTA.G.sub.3 each are extremely small, compared with acceleration G.sub.sb, G.sub.sa while .DELTA.G.sub.1 and .DELTA.G.sub.4 is not so small. Therefore, amplification of .DELTA.G is desirable.
The signal processing circuit 12 adjusts the acceleration difference .DELTA.G to be a constant offset value according to an instruction of the CPU 13. The adjustment of the offset should preferably be effected during stoppage of the automobile when the automobile angular rate is detected.
The digital potentiometers 11, 15, 21 can be changed in resistance value R.sub.1, R.sub.2, R.sub.5 by the CPU 13. The potentiometers 11 and 15 are used for adjusting a resistance part of the CR filter and the potentiometer 21 is used for making an offset value constant.
According to FIG. 8, the signal processing circuits 10, 12 output signals from which noises are removed from output of the acceleration sensors. The signals are inputted directly into the CPU 13. Further, the signals are inputted into the signal processing circuit 12 to obtain a difference therebetween and amplify it. The amplified difference is inputted into the CPU to calculate angular rate .omega.. The circuit 12 controls the offset value to be constant, so that the result is not influenced badly by variations in preciseness of the acceleration sensors 2, 3.
First of all, a port F is made high in step 30. Next, it is checked whether or not a starter is rotating in step 31. When the starter is not rotating, it is checked whether or not the car speed is 0 in step 32. In this case, when the car speed is not 0, the processing is returned, because a car speed which is not zero means that the car is running, and the value in such a case can not be used as an initial value. When the starter is rotating and the car speed is zero, an amplified difference output V.sub.out in the signal processing circuit 12 is read into CPU 13 at step 33. The output is checked to see whether or not it is larger than a predetermined value V.sub.01 in step 34, and when the output V.sub.out is larger than the predetermined value V.sub.01, the port E is made low in step 16 and the port F is made low in step 38 whereby the resistance of the potentiometer 21 is decremented. When the amplified difference output V.sub.out is judged to be smaller than another predetermined value V.sub.02 which is smaller than V.sub.01 (V.sub.01 >V.sub.02) in step 35, the resistance of the potentiometer 21 is incremented by making the port E high in step 37 and by making the port F low in step 39. In step 35, the amplified difference output V.sub.out is not smaller than the predetermined value V.sub.02, that is, when V.sub.02 .ltoreq.V.sub.out .ltoreq.V.sub.01, it is thought that the offset value is proper, and the offset control is completed.
Decrementing of the resistance of the potentiometer 21 in steps 36, 38 or incrementing of the resistance in steps 37, 39 are repeated at each time of the interruption, for example, 10 msec, until the condition V.sub.02 .ltoreq.V.sub.out .ltoreq.V.sub.01 is satisfied. In this case, U/D takes two values, Low and High. In order to coincide U/D with FIG. 8, "U" means Low and "D" means High.
Assuming that V.sub.01 -V.sub.02 =.epsilon. (allowable error), a value of .epsilon. determines magnitude of error in the amplified difference output. That is, the larger the value .epsilon., the larger the error.
The arithmetic operation itself of the equation (8) or (10) is not described. The equation (8) or (10) can be calculated directly, or a relationship between the acceleration difference .DELTA.G and an angular rate corresponding thereto can be stored in a map table as shown in FIG. 10 and the corresponding angular rate .omega.i can be obtained from .DELTA.Gi.
Examples in which acceleration sensors are mounted on an automobile are shown in FIGS. 11A, 11B and 11C. Each of the examples have two pairs of the acceleration sensors. In FIG. 11A, the acceleration sensors A.sub.1, B.sub.1 are mounted on front and rear portions of the automobile, respectively. The acceleration sensors A.sub.2, B.sub.2 are mounted on a roof and a floor of the automobile, respectively. Any of the pairs of the acceleration sensors A.sub.1, B.sub.1 ; A.sub.2, B.sub.2 can detect a pitch rate of the automobile. Assuming that a forward and backward direction of the automobile is an x-direction in a x-y plane parallel to the ground, the pitch means rotation around a y-axis perpendicular to the x axis.
In order to calculate a pitch rate, a difference between outputs of the acceleration sensors A.sub.1, B.sub.1 is detected and then the pitch rate is calculated, based on the difference and a distance between the acceleration sensors A.sub.1, B.sub.1. In a similar manner, the pitch rate also can be obtained using output difference of the acceleration sensors A.sub.2, B.sub.2 and a positional distance between the acceleration sensors A.sub.2, B.sub.2 and according to the equation (8) or (10).
In FIG. 11B, examples of an arrangement of the pair of acceleration sensors A.sub.1, B.sub.1 and a pair of acceleration sensors A.sub.3, B.sub.3 for obtaining a yaw rate of an automobile are shown. Each pair of the sensor A.sub.1, B.sub.1 ; A.sub.3, B.sub.3 can detect a yaw rate. In FIG. 11B, the sensors A.sub.3, B.sub.3 are mounted on sides of the automobile, respectively. Yaw rate refers to rotational angular rate around a z axis perpendicular to the x-y plane, which is the running ground. A method of calculation for obtaining the yaw rate is similar to the method of obtaining the pitch rate.
FIG. 11C shows an example of an arrangement of acceleration sensors for obtaining a roll rate. The acceleration sensors A.sub.2, B.sub.2 have a similar arrangement to sensors A.sub.2, B.sub.2 in FIG. 11A. Namely they are mounted on the roof and the floor of the automobile so that a detection direction of acceleration is vertical. Another pair of acceleration sensors A.sub.3, B.sub.3 also are arranged on the automobile in a similar fashion to sensors A.sub.3, B.sub.3 in FIG. 11B, that is they are mounted on the sides of the automobile so that the acceleration detection directions are the same. Each pair of the acceleration sensors can detect a roll rate. The roll rate is rotational angular rate around a y axis which is parallel to a running direction of the automobile. The arithmetic operation for obtaining the angular rate, that is, the roll rate around the y axis is effected according to the equation (8) or (10).
In this arrangement of the acceleration sensors 2, 3, angle .theta.a is relatively close to angle .theta.b as compared with one shown in FIG. 1. Therefore, an output difference from the acceleration sensor 2, 3 used for calculation of angular rate is small, so that it is preferable to provide amplifying means.
As for a control employing a yaw rate, there is an anti-skid brake control apparatus and a 4-wheel steering control apparatus. The anti-skid brake control apparatus prevents locking of the wheel and suppresses occurrence of yaw which is not intended by a driver, using a detected yaw rate. The 4-wheel steering control apparatus controls rear wheels of an automobile so that detected yaw rate reaches a target value. The control apparatus is shown in FIG. 14, and includes a control section 43 comprising a control input calculation part 44 and a yaw rate arithmetic operation part 45, and an actuator 46. In this control apparatus, acceleration sensors (not shown) mounted on a car body 47 output acceleration outputs G.sub.sa, G.sub.sb detected thereby. The acceleration outputs, G.sub.sa, G.sub.sb are inputted into the yaw rate arithmetic operation part 45 to calculate a yaw rate of the car body. The yaw rate is compared with a target yaw rate to obtain a difference. The control input calculation part 44 calculates a control input according to the difference and outputs a control input. The actuator 46 actuates brakes in the anti-skid brake control apparatus according to the control input from the control input calculation part 44, and rear wheels in the 4-wheel steering control apparatus thereby to control movement of the car body. The operation is repeated, whereby the yaw rate approaches the target yaw rate.
This is explained referring to FIG. 1. Here, acceleration of parallel movement of the moving body 1 at the center of gravity thereof is obtained with a high preciseness. Assuming that acceleration at the center of gravity is G.sub.c. The acceleration G.sub.c is given as follows:
G.sub.c =G.sub.la =G.sub.lb (11)
G.sub.c =G.sub.sa -G.sub.ya cos .theta.a (12)
Here, G.sub.ya =R.sub.a.omega..sup.2. The equation (12) is converted as follows using the equation (12): ##EQU6## The equation (13) is simplified as follows: ##EQU7## According to the equation (14), acceleration due to centrifugal force of rotational movement of the moving body is cancelled, and parallel acceleration at the center 4 of gravity can be obtained.
Hitachi Automotive Engineering Incorporated (Hitachi, Ltd.), Hitachi, Ltd.
Nakamura, Yozo, Monji, Tatsuhiko, Shimada, Kousaku, Sugawara, Hayato, Horikoshi, Shigeru
364/566, 364/453, 364/424.01, 73/510-512, 73/517 A
B60G 2400/1042 : using at least two sensors
B60G 2400/1062 : using at least two sensors
B60T 2250/03 : Vehicle yaw rate
G01P 3/44 : for measuring angular speed...
Current Assignee: Hitachi Automotive Engineering Incorporated (Hitachi, Ltd.), Hitachi, Ltd.
Sponsoring Entity: Hitachi Automotive Engineering Incorporated (Hitachi, Ltd.), Hitachi, Ltd.