METHOD FOR ASCERTAINING MOVEMENT VARIABLES OF A TWO-WHEELED VEHICLE

Abstract

A method for ascertaining movement variables of a two-wheeled vehicle. The two-wheeled vehicle includes a sensor system including rotational rate, acceleration, and wheel rotational speed sensors. The wheel rotational speed sensor detects at least one measurement pulse per rotation of a wheel of the two-wheeled vehicle. The method includes: acquisition of three-dimensional rotational rates of the two-wheeled vehicle by the rotational rate sensor, acquisition of acceleration values by the acceleration sensor, estimation of a state of movement of the two-wheeled vehicle based on the acquired rotational rates, the state of movement including estimated values for estimated acceleration values and for an estimated speed and for an estimated distance traveled, first correction of the estimated state of movement based on the acquired acceleration values, and ascertaining of an instantaneous speed of the two-wheeled vehicle and/or of a distance traveled by the two-wheeled vehicle, based on the corrected estimated state of movement.

Claims

1. A method for ascertaining movement variables of a two-wheeled vehicle, the two-wheeled vehicle including a sensor system that has a rotational rate sensor, an acceleration sensor, and a wheel rotational speed sensor, the wheel rotational speed sensor being configured to detect at least one measurement pulse per rotation of a wheel of the two-wheeled vehicle, the method comprising the following steps: acquiring three-dimensional rotational rates of the two-wheeled vehicle, by the rotational rate sensor; acquiring acceleration values of the two-wheeled vehicle by the acceleration sensor; estimating a state of movement of the two-wheeled vehicle based on the acquired rotational rates, the state of movement including estimated values for estimated acceleration values, for an estimated speed, and for an estimated distance traveled; a first correcting of the estimated state of movement based on the acquired acceleration values; and ascertaining an instantaneous speed of the two-wheeled vehicle and/or a distance traveled by the two-wheeled vehicle, based on the corrected estimated state of movement.

2. The method as recited in claim 1, further comprising the following step: a second correcting of the estimated state of movement based on the measurement pulses detected by the wheel rotational speed sensor.

3. The method as recited in claim 2, wherein the second correction is carried out based on the following equation: y2=[x5, old+2 πr] with a corrected value y2 for the distance traveled by the two-wheeled vehicle, an old value x5, old for the distance traveled by the two-wheeled vehicle, and a radius r of a wheel of the two-wheeled vehicle.
y2=[x5,old+2πr]

4. The method as recited in claim 1, wherein one or more of the following movement variables of the two-wheeled vehicle being ascertained based on the corrected estimated state of movement: roll angle, pitch angle, longitudinal acceleration.

5. The method as recited in claim 1, wherein the first correction is carried out using a non-linear Kalman filter.

6. The method as recited in claim 1, the estimation of the state of movement of the two-wheeled vehicle takes place using a state vector $x=\left[\begin{array}{c}x1\\ x2\\ x3\\ x4\\ x5\end{array}\right],$ with a roll angle x1, a pitch angle x2, a longitudinal acceleration x3, a longitudinal speed x4, and a distance traveled x5, and using an input vector $u=\left[\begin{array}{c}u1\\ u2\\ u3\end{array}\right],$  with the three-dimensional rotational rates u1, u2, and u3, and based on the following system equation: $\dot{x}=\left[\begin{array}{c}u1+\tan \left(x2\right)\sin \left(x1\right)u2+\tan \left(x2\right)\cos \left(x1\right)u3\\ \cos \left(x1\right)u2-\sin \left(x1\right)u3\\ 0\\ x3\\ x4\end{array}\right].$

7. The method as recited in claim 6, wherein the estimation of the state of movement of the two-wheeled vehicle takes place based on a calculation of an integral of the system equation {dot over (x)}.

8. The method as recited in claim 7, the estimation of the state of movement of the two-wheeled vehicle further being carried out based on the following equations: $\mathrm{Rx}=\left[\begin{array}{ccc}1& 0& 0\\ 0& \cos \left(x1\right)& \sin \left(x1\right)\end{array}\right],$ $\mathrm{Ry}=\left[\begin{array}{ccc}\cos \left(x2\right)& 0& -\sin \left(x2\right)\\ 0& 1& 0\\ \sin \left(x2\right)& 0& \cos \left(x2\right)\end{array}\right],$ $\dot{\psi }=\frac{\left(u2\sin \left(x1\right)+u3\cos \left(x1\right)\right)}{\cos \left(x2\right)},$ $y1=RxRy\left[\begin{array}{c}x3\\ -x4\dot{\psi }\\ g\end{array}\right].$ with a yaw rate {dot over (ψ)} of the two-wheeled vehicle and the estimated acceleration values y1 of the two-wheeled vehicle.

9. The method as recited in claim 1, further comprising the step: ascertaining a standstill of the two-wheeled vehicle based on the estimated state of movement.

10. The method as recited in claim 6, further comprising the following steps: reducing the state vector x and the system equation {dot over (x)} to the following states: $x=\left[\begin{array}{c}x1\\ x2\end{array}\right]\mathrm{and}$ $\dot{x}=\left[\begin{array}{c}u1+\tan \left(x2\right)\sin \left(x1\right)u2+\tan \left(x2\right)\cos \left(x1\right)u3\\ \cos \left(x1\right)u2-\sin \left(x1\right)u3\end{array}\right],$ when the wheel rotational speed sensor detects no measurement pulses over a prespecified period of time, or if a standstill of the vehicle has been ascertained, and expanding the state vector x and the system equation {dot over (x)} to the original states before the reduction when measurement pulses are again detected by the wheel rotational speed sensor.

11. The method as recited in claim 1, further comprising the following step: ascertaining a steering angle of the two-wheeled vehicle based on the corrected estimated state of movement.

12. The method as recited in claim 8, further comprising the following step: ascertaining a steering angle δ of the two-wheeled vehicle based on the corrected estimated state of movement; wherein the ascertaining of the steering angle δ is carried out based on the following equation: $\delta =\arctan \left(\frac{\stackrel{.}{\psi }L}{x4}\right),$  with a wheelbase L of the two-wheeled vehicle (1).

13. A two-wheeled vehicle, comprising: a sensor system including a rotational rate sensor, an acceleration sensor, and a wheel rotational speed sensor; and a control device configured to: acquire three-dimensional rotational rates of the two-wheeled vehicle, using the rotational rate sensor, acquire acceleration values of the two-wheeled vehicle using the acceleration sensor, estimate a state of movement of the two-wheeled vehicle based on the acquired rotational rates, the state of movement including estimated values for estimated acceleration values, for an estimated speed, and for an estimated distance traveled, a first correction of the estimated state of movement based on the acquired acceleration values; and ascertain an instantaneous speed of the two-wheeled vehicle and/or a distance traveled by the two-wheeled vehicle, based on the corrected estimated state of movement.

14. The two-wheeled vehicle as recited in claim 13, wherein the two-wheeled vehicle is an electrically driven bicycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the following, the present invention is described on the basis of exemplary embodiments in connection with the Figures. In the Figures, functionally identical components have been identified with the same reference characters.

[0032] FIG. 1 shows a simplified schematic view of a two-wheeled vehicle having a sensor system and a control device for carrying out a method according to a preferred exemplary embodiment of the present invention.

[0033] FIG. 2 shows an alternative view of the two-wheeled vehicle of FIG. 1 in order to illustrate a steering angle.

[0034] FIG. 3 shows an alternative view of the two-wheeled vehicle of FIG. 1 in order to illustrate an inclined position.

[0035] FIG. 4 shows a simplified schematic view of the carrying out of a method according to the preferred exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0036] FIG. 1 shows a simplified schematic view of a two-wheeled vehicle 1 having a sensor system 2 and a control device 20 for carrying out a method for ascertaining movement variables of two-wheeled vehicle 1 according to a preferred exemplary embodiment of the present invention.

[0037] Two-wheeled vehicle 1 is an electric bicycle that has, in the area of a bottom bracket bearing, a drive unit 12 by which a manually produced pedaling force of a driver of two-wheeled vehicle 1 can be motorically supported. Drive unit 12 is provided with electrical energy by an electrical energy storage device 14.

[0038] Control device 20 is situated on a steering handle of two-wheeled vehicle 1, and can for example be part of an onboard computer.

[0039] Sensor system 2 has a plurality of sensors. In detail, sensor system 2 has a rotational rate sensor 21 and an acceleration sensor 22, both of which are integrated into control device 20.

[0040] Rotational rate sensor 21 acquires three-dimensional rotational rates of two-wheeled vehicle 1 during travel. A rotational rate is acquired about each of the axes x, y, z indicated in FIG. 1 (see also FIGS. 2 and 3).

[0041] Here, the x axis is parallel to a longitudinal axis L of two-wheeled vehicle 1 (see FIG. 2) that, during straight-line travel of two-wheeled vehicle 1, is parallel to a direction of travel A. The z axis corresponds to a vertical axis H (see FIG. 3) that is in particular parallel to a direction of gravitation (not shown) of the Earth's gravitational field. The y axis is perpendicular to the x axis and perpendicular to the z axis. The y axis can also be referred to as the pitch axis. The z axis can also be referred to as the yaw axis.

[0042] Acceleration sensor 22 acquires acceleration values of two-wheeled vehicle 1, preferably a total of three acceleration values along each of the axes x, y, z.

[0043] In addition, sensor system 2 includes a single-pulse wheel rotational speed sensor 23 that is designed as a rotation sensor in order to detect exactly one measurement pulse per rotation of a wheel 11 of two-wheeled vehicle 1. For this purpose, wheel rotational speed sensor 23 is set up to detect the measurement pulse exactly once per rotation of wheel 11, each time that a magnet 23a, fastened for example to a spoke of wheel 11, passes by. Based on the measurement pulses detected by wheel rotational speed sensor 23, in this way a rotational speed of wheel 11 can be ascertained.

[0044] Using method 50, an instantaneous speed of two-wheeled vehicle 1, a distance traveled, and an instantaneous steering angle δ are ascertained as movement variables of two-wheeled vehicle 1.

[0045] Steering angle δ is illustrated in FIG. 2. FIG. 2 shows a view of two-wheeled vehicle 1 along the z axis. As can be seen in FIG. 2, steering angle δ corresponds to an angle between longitudinal axis L and front wheel 11. During travel straight ahead, steering angle δ is equal to zero, and becomes correspondingly higher the smaller a radius of the curve traveled through by two-wheeled vehicle 1 becomes.

[0046] During travel in a curve with two-wheeled vehicle 1, two-wheeled vehicle 1 is brought into an inclined position, as shown in FIG. 3. FIG. 3 schematically shows an angle of inclination β of two-wheeled vehicle 1. Angle of inclination β is the angle by which two-wheeled vehicle 1 is inclined out of vertical axis H.

[0047] In the following, the carrying out of method 50 for ascertaining the movement variables of two-wheeled vehicle 1 is described with reference to FIG. 4.

[0048] In method 50, first the rotational rate sensor 21 acquires 51 the three-dimensional rotational rates of two-wheeled vehicle 1. At the same time, the acceleration values of two-wheeled vehicle 1 are acquired 52 by acceleration sensor 22. Based on the acquired three-dimensional rotational rates, there subsequently takes place an estimation 53 of a state of movement of two-wheeled vehicle 1.

[0049] The state of movement of two-wheeled vehicle 1 includes estimated values for estimated acceleration values and for an estimated speed, and also for an estimated distance traveled. In detail, the estimation of the state of movement takes place using a state vector that has the following parameters: roll angle, pitch angle, longitudinal acceleration, longitudinal speed, and distance traveled. In particular, here the roll angle corresponds to the angle of inclination β, i.e. a deflection or rotation of two-wheeled vehicle 1 about vertical axis H. Preferably, the pitch angle corresponds to a deflection or rotation of two-wheeled vehicle 1 about the y axis, i.e., transverse to vertical axis H.

[0050] Based on the state vector and an input vector, the input vector having the three-dimensional rotational rates, a system equation is subsequently created that represents in particular a temporal change of the state vector.

[0051] Subsequently, the state of movement of two-wheeled vehicle 1 is estimated 53 by calculating an integral of this system equation. As a result, the estimated movement variables of two-wheeled vehicle 1 are obtained.

[0052] There subsequently follow correction steps 54, 55 of the state of movement. First, there takes place a first correction 54 of the state of movement based on the acceleration values actually acquired by acceleration sensor 22.

[0053] In addition, a second correction 55 of the state of movement takes place every time a measurement pulse of wheel rotational sensor 23 is detected. In detail, the state of movement is here corrected based on the distance actually traveled, ascertained by wheel rotational speed sensor 23. Because the distance actually traveled can be determined very accurately based on the geometrical relationship of the measurement pulses to the wheel circumference of wheel 11, second correction 55 can carry out a particularly accurate correction step of the state of movement.

[0054] Subsequently, based on the corrected state of movement, steering angle δ of two-wheeled vehicle 1 can be ascertained 57.

[0055] Moreover, method 50 can be carried out in a modified form (not shown) that additionally takes into account a standstill of two-wheeled vehicle 1. Here, in addition an ascertaining of a standstill of two-wheeled vehicle 1 takes place based on the estimated state of movement.

[0056] When a standstill of two-wheeled vehicle 1 has been ascertained, the state vector and the system equation can be reduced to the first two states. In this way, the estimated movement variables can be prevented from drifting as time progresses due to the absence of a measurement pulse that can be used for second correction 55. As soon as it has been ascertained that two-wheeled vehicle 1 is again moving, or as soon a measurement pulse has again been ascertained by wheel rotational speed sensor 23, the state vector and the system equation are again expanded to the original states before the reduction, so that subsequently an accurate determination of all the movement variables is again enabled.

[0057] Alternatively to a standstill of two-wheeled vehicle 1, an absence of a measurement pulse of wheel rotational speed sensor 23 can also be used to reduce the state vector and the state equation to the first two states.

[0058] The state of movement, corrected once or twice, thus has particularly accurate estimated values for the movement variables of two-wheeled vehicle 1. In particular, in this way on the basis of the corrected state of movement a desired movement variable, such as the speed, can be read off at any desired time and for example used for further systems or methods of two-wheeled vehicle 1. In addition, using method 50 the movement variables of two-wheeled vehicle 1 can be precisely ascertained even at very low speed, because method 50 is based in particular on the measurement values of rotational rate sensor 21 and acceleration sensor 22, which are capable of supplying precise and reliable measurement values even at low speeds.