GB2530380A

GB2530380A - Device and method for generating a speed value

Info

Publication number: GB2530380A
Application number: GB1512360.7A
Authority: GB
Inventors: Daniel Baumgaertner; Tim Dackermann; Gregor Dasbach
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-07-17
Filing date: 2015-07-15
Publication date: 2016-03-23
Anticipated expiration: 2035-07-15
Also published as: DE102014213943A1; GB2530380B; GB201512360D0

Abstract

A method for generating an output value which represents a speed value, having the steps of: acquiring a first and second signal and generating a first speed value in dependence on the first and second signal, further having the following step: starting a measurement with a first measuring duration in dependence on the first speed value and outputting an output value, wherein, in the case where a third signal is acquired during the first measuring duration, a second speed value in dependence on the second and third signal is outputted as output value and in the case where a third signal is not acquired during the first measuring duration, a zero value is outputted as output value. The method is said to be particularly useful in the control of an electric bicycle, giving an improved response time in identifying a zero speed.

Description

Description Title

Device and method for generating a speed value

Field of the invention

The present invention relates to a method and a device for generating an output value which represents a speed value and to an electric bicycle.

Prior art

Methods for determining speeds in particular for bicycles are known from the prior art. Furthermore, speed indicators which are suitable for outputting speed values are known.

Moreover, devices for processing measured signals are known, in which the speed or a movement state of the bicycle can be inferred by an evaluation of the measured signals generated on a bicycle.

Thus, for example, in DE 60 2005 001 275 T2 there is disclosed a pedalling frequency sensor, in which magnetic signals of a magnet rotating past a sensor are captured by means of the sensor. The magnet is situated on a spoke of a rear wheel of a bicycle. Furthermore, if an automatic stop mode is set, a time counter can stop provided that no further wheel rotation is detected over a defined period.

The time which elapses between the instant at which a cyclist stops moving and the instant at which a system interprets that a stop has occurred is, in a preferred embodiment in the prior art cited above, 8 seconds from the last wheel rotation detected.

Disclosure of the invention

The invention relates to a method and a device for generating an output value which represents a speed value.

In this regard, a first and a second signal are acquired and in dependence on the first and second signal there is generated a speed value which can be outputted as output value or taken as a base value for further data processings. The device has a processing unit for carrying cut the method.

The invention further relates to an electric bicycle. The electric bicycle comprises a device suitable for generating an output value which represents a speed value. The device is preferably suitable for carrying out the method according to the invention. In particular, the device is the device according to the invention.

The essence of the invention consists in that a measurement with a first measuring duration in dependence on the first speed value is started and then an output value is outputted. Here, in the case where a third signal is acquired during the first measuring duration, a second speed value in dependence on the second and the third signal is outputted as output value. In the case where a third signal is not acquired during the first measuring duration, a zero value is outputted as output value.

A measuring duration adapted to the current speed value results in the advantage that the information about the stopping of the bicycle, the speed value of which is to be outputted, can be outputted more quickly owing to a shorter dead time. The dead time is a period during which a last ascertained speed value is displayed. The more quickly outputted output value can then be utilised more quickly and used to control a motor or displayed as a speed value on a speedometer display. The more quickly outputted output value can be utilised, for example, in an evaluation of the average speed in a sport display. Since the dead time is shorter, the average speed and the total cycling time can be determined more accurately. In the case where the output value is used to control a motor, a braking or a starting can be performed more quickly using the real speed as a result of the earlier controlling of the motor.

According to one embodiment of the invention, in the case where the previous output value is greater, for example 5% to 201 greater, than the current output value, the next measuring duration is lengthened, in particular by 5% to 20%, in comparison with the current measuring duration.

According to one embodiment of the invention, in the case where the previous output value is less, for example 5% to 20% less, than the current output value, the next measuring duration is shortened, in particular by 5% to 20%, in comparison with the current measuring duration.

The fact that the next measuring duration is shortened has the result in particular that, at high speed values, a complete stopping of a vehicle can be detected more quickly.

According to a further embodiment of the Invention, an acceleration quantity is acquired. Subsequently a comparison speed value in dependence on the acceleration quantity is calculated. Finally the current output value is reduced, for example by 10%, if the last ascertained speed value is greater, for example 10% greater, than the comparison speed value. The current output value is increased, for example by 10%, if the last ascertained speed value is less, for example 10%: less, than the comparison speed value.

The comparison speed vaiue thus serves for checking the speed value with regard to its reliability. The comparison speed value is suitable for this checking of the speed value, since it can be calculated with the aid of an acceleration quantity measurable independently of the measurement of the speed value. A MEMS sensor is suitable for measuring an acceleration quantity.

For the purpose of this checking of the speed value with the aid of the comparison speed value it can be checked whether the speed value deviates from the comparison speed value by a total or relative proportion. This can be a relative proportion of 10%. If the speed value deviates by more than 10% from the comparison speed value, the speed value is classified as incorrect. The current output value is then corrected and adapted in dependence on the comparison speed value. The degree of adaptation of the current output value can be dependent on how great the relative or total deviation of the speed value is from the comparison speed value.

The correction of the current output value results in an increase in the reliability of the method and of the application of the device. The correct current output value, which represents the correct actual speed value, can be used to control a motor to match the actual speed of the vehicle or be displayed as a speed value on a speedometer display. Furthermore, it can be used as an actual speed value for an evaluation of the data about the speed values, for example for an evaluation for sport purposes.

According to a next embodiment of the invention, a fixed minimum speed measuring duration or a fixed maximum speed measuring duration is set in dependence on the last ascertained speed value and a fixed speed minimum value and/or a fixed speed maximum value. The speed minimum value is in particular 2.5 km/h, the speed maximum value is in particular 25 km/h. In the case where the last ascertained speed value lies below the fixed speed minimum value of for example 2.5 km/h, a fixed minimum speed measuring duration of 3 seconds is set. Furthermore, in the case where the last ascertained speed value lies above the fixed speed maximum value of for example 25 km/h, a fixed maximum speed measuring duration of 0.3 seconds is set.

According to this embodiment, in partidillar variable speed maximum values and variable speed minimum values can be used.

The rationale behind this setting of a fixed measuring duration is that in the case of high speeds the speed output no longer needs to be adapted, since the outputting of the output value already takes place sufficiently quickly enough for the purposes of a motor control. Also, the processing speed with which the motor control can process the output values can be lower than the output speed, a higher output speed is in this case useless.

Furthermore, at high speeds the increase of the output speed may be ineffective, since the displaying of the outputted output value on a speedometer display itself takes place with a slower speed than is possible based on the speed of the outputting of the output values.

In the case of low speeds, for example in a speed range shortly before the stopping of the bicycle, the measuring duration adapted to the speed and the associated output speed of the output value is likewise unnecessary, since there is no need for the information about the speed or for the assistance by a motor. The rationale behind the fact that there is no need for assistance by a motor is that an automatically motor-assisted drive of the bicycle by a motor assistance in the case of slow speeds, for example less than 2.5 km/h, should not occur. The automatically motor-assisted drive of the bicycle may result in an uncontrolled movement of the bicycle for the rider of the bicycle. JAn uncontrolled movement of the bicycle involves a risk of injury to the rider.

Further advantageous embodiments of the invention are subj cot matter of the subclaims.

Brief description of the figures

Figure 1 shows the schematic representation of a method according to the invention; Figure 2 shows the schematic representation of a device according to the invention; Figure 3 shows the schematic representation of a relationship between an actual speed and a current measuring duration according to an embodiment of the invention; Figure 4 shows the schematic representation of a relationship between a measuring duration and a speed value according to an embodiment of the invention.

Exemplary embodiments The invention is explained below with the aid of exemplary embodiments, from which there may arise further inventive features, to which the invention is not limited in its scope. Some exemplary embodiments are represented in the figures.

In Figure 1 a method according to the invention is schematically represented. The background of the method according to the invention is the generation of a speed value during speed measurement in the case of a bicycle, in particular an E-bike. In the case of a bicycle, a speedometer is situated on the bicycle to generate a speed value of the bicycle. The speedometer evaluates signals, the signals being generated by means of a measuring device for measuring a magnetic signal and a magnet which is attached to a spoke of a wheel. The measuring device is attached to a fork of the bicycle. As a result of the magnet moving past the measuring device on a circular path, a time difference between two signals and thus the speed of the magnet on the wheel is determined. In dependence on the time difference, the speed of the bicycle can be calculated if the circumference of the wheel is known.

If the bicycle comes to a complete stop within the measuring duration from the last acquired signal, then for the period of the measuring duration which has not yet elapsed the last ascertained speed value is outputted. The aim of the invention is therefore a measuring duration adapted to the current speed of the bicycle. By adapting the measuring duration to the speed, the complete stopping of the bicycle can be detected more quickly and the information outputted.

The method is automatically started. In acquisition step 1, a first and a second signal are acquired. The first and the second signal are in particular the magnetic signals which are generated by means of the magnet moving past the measuring device. In the following generation step 2, a first speed value is generated in dependence on the first and second signal. In the following measurement step 3, a measurement for the acquisition of a third signal is started. The measurement is started with a first measuring duration. By way of example, a measuring duration lies between 0.3 seconds and 3 seconds. The measuring duration depends on the first speed valile. In the case where a third signal is not acquired during the first measuring duration, a zero value is outputted as output value in the zero output step 4. The output preferably takes place on a display device A of a speedometer. In the case where a third signal is acquired during the first measuring duration, a second speed value in dependence on the second and third signal is outputted as output value in the output step 5. In end step 6, the method is ended after zero output step 4 or output step 5. For example, the method can be ended by switching off the measuring device. The method can be repeated after the end step 6.

A polynomial relationship can exist between the first measuring duration and the first speed value. In particular, it can be a polynomial relationship of first, second or third degree. The higher the order of the polynomial relationship, the quicker the output value is outputted, with the result that at high speeds a rapid, sharp braking can be detected and taken into account all the quicker. If the case of repeated carrying-out of the method occurs, a next measuring duration is generally assigned to a last ascertained speed value. During the next measuring duration, a current speed value is outputted. The speed value, in dependence on which the next measuring duration is brought about, can be referred to as last ascertained speed value.

The relationship between the next measuring duration and the last ascertained speed value can be such that with increasing speed values the next measuring duration decreases, for example by 5% to 20%, or that with decreasing speed values the next measuring duration increases, for example by 5% to 20%.

The circumstance whether the speed values decrease or increase can be determined by a comparison between the respectively current speed value and the respectively last ascertained speed value.

Tn Figure 2 a device V for generating an output value which represents a speed value is schematically represented. The device V has a processing unit VA for carrying out the method according to the invention. The processing unit VA acquires a first and a second sensor-detected signal. The signals can be detected by means of a sensor Si and transmitted to the processing unit VA by means of a line.

The sensor Si can be a magnetic sensor. The processing unit VA generates a first speed value in dependence on the first and second signal. A second sensor 52 can be an acceleration sensor or a speed sensor. The acceleration sensor can be a MEMS acceleration sensor.

Finally, the processing unit VA starts a measurement with a first measuring duration and outputs an output value via a connection, wireless or wired. The measuring duration depends on the first speed value. By way of example, a measuring duration lies between 0.3 seconds and 3 seconds.

Tn the case where a third signal is not acquired during the first measuring duration, a zero value is outputted as output value. In the case where a third signal is acquired during the first measuring duration, a second speed value in dependence on the second and third signal is outputted as output value. The output value can be outputted from the processing unit VA by means of a connection and transmitted to a display A and displayed there as speed value. For processing control signals, a motor control can be situated inside or outside the processing unit VA. The control signals can be transmitted to a motor M via a connection.

In Figure 3 a relationship between an actual speed v -for example of a bicycle -and two measuring durations is schematically represented. In this exemplary embodiment the speed v decreases linearly, see 200, and reaches a zero value at the instant tN. At the instant tN the bicycle has completely stopped. The complete stopping of the bicycle can be detected at the instant ti or t2 depending on the choice of the measuring duration. The information about the complete stopping of the bicycle can accordingly be outputted and used at different instants as output value.

At the instant tO the bicycle had the speed vz. The speed vz is outputted as output value and displayed on a i1 speedometer. At the instant tO the measurement is started.

The measuring duration of the measurement can be ti-tO or t2-tO. The measuring duration t2-tO is longer than measuring duration ti-tO, the complete stopping of the bicycle is detected at a later instant, see 220, and the information about the complete stopping of the bicycle can be outputted later. In the case of the shorter measuring duration ti-tO the complete stopping of the bicycle is detected at an earlier instant, see 210, and can be outputted earlier. Either after the measuring duration ti-to or t2-tO has elapsed, the speed value vz is outputted as output value, depending on which measuring duration the measurement is based, the information about the complete stopping of the bicycle is outputted earlier or later. The next measurement is started with a measuring duration, the measuring duration depending on the speed value vz.

Tn Figure 4 a relationship, according to the invention, between a measuring duration t and a speed value v -which represents for example a speed of a bicycle -is schematically represented. In this exemplary embodiment, for speed values v less than vi a fixed measuring duration t2 is set; see 300. The rationale behind the fixed measuring duration is that at low speeds, for example when the bicycle is decelerating, up to a desired stopping of the bicycle, a measuring duration adapted to the speed and an associated increased output speed of the output value is unnecessary, since there is no need for the information about the speed. There is no need for the information because the rider is aware of the slow speed and can estimate this well himself or herself. For speed values v which are greater than a speed value vi but less than v2, there is a linear relationship, see 310, between the measuring duration t and the speed value v. The greater the speed vaiue v, the iess the measuring duration t becomes.

As a result, the speed values are outputted more quickly and speed changes at high speed can be detected more quickly. If the speed value v lies above a speed value v2, the measuring duration t is assigned the fixed value ti, see 320. The rationale behind the fixed measuring duration tl is that at high speeds the increase of the output speed may be ineffective, since the displaying of the outputted output value on a speedometer display itself takes place with a slower speed than is possible based on the speed of the outputting of the output values. A higher output speed may also be ineffective for the purpose of a motor control, if the motor control or the motor itself reacts more slowly than is necessary for processing output values outputted more quickly.

The dot-dash line 330 represents a constant course of the measuring duration t according to the prior art. According to this constant course, the measuring duration t has a fixed value t2; irrespective of the last ascertained speed value, the next speed value is outputted as output value after the measuring duration t2.

Claims

Claims 1. Method for generating an output value which represents a speed value, having the following steps: -acquiring a first and second signal and -generating a first speed value in dependence on the first and second signal, characterised by the following step: -starting a measurement with a first measuring duration in dependence on the first speed value and outputting an output value, wherein, in the case where a third signal is acquired during the first measuring duration, a second speed value in dependence on the second and third signal is outputted as output value and in the case where a third signal is not acguired during the first measuring duration, a zero value is outputted as output value.
2. Method according to Claim 1, wherein, in the case were the previous output value is less than the current output value, the next measuring duration is shortened in comparison with the current measuring duration.
3. Method according to Claim 2, wherein the next measuring duration is shortened by 5% to 20%.
4. Method according to one of Claims 1 to 3, wherein, in the case where the previous output value is greater than the current output value, the next measuring duration is lengthened in comparison with the current measuring duration.
5. Method according to Claim 4, wherein the next measuring duration is lengthened by 5% to 20%.
6. Method according to one of the preceding claims, having the further steps -acquiring an acceleration quantity, -ca'culating a comparison speed value in dependence on the acceleration quantity, -reducing the current output value, for example by 10%, if the last ascertained speed value is greater, for example by 10%, than the comparison speed value or increasing the current output value, for example by 10%, if the last ascertained speed value is less, for example by 10%, than the comparison speed value.
7. Method according to one of the preceding claims, having the further step -setting a fixed minimum speed measuring duration, for example 3 seconds, in the case where the last ascertained speed value lies below a fixed speed minimum value, in particular of 2.5 km/h, and a fixed maximum speed measuring duration, for example 0.3 seconds, in the case where the last ascertained speed value lies above a fixed speed maximum value, in particular of 25 km/h.
8. Device (V) for generating an output value which represents a speed value, having a processing unit (VA) which is suitable in particular for carrying out a method according to Claim 1 to 7, and wherein the processing unit (VA) -acquires a first and a second sensor-detected signal, -generates a first speed value in dependence on the first and second signai, characterised in that the processing unit (VA) -starts a measurement with a first measuring duration in dependenoe on the first speed value and outputs an output value, wherein in the case where a third signal is acguired during the first measuring duration, a second speed value in dependence on the second and the third signal is outputted as output value and in the case where a third signal is not acquired during the first measuring duration, a zero value is outputted as output value.
9. Device (V) according to Claim 8, characterised in that the processing unit (VA) , in the case were the previous output value is less than the current output value, shortens the next measuring duration in comparison with the current measuring duration, in particular by 5% to 2 0 1.
10. Device (V) according to Claim 8 or 9, characterised in that the processing unit (VA) , in the case where the previous output value is greater than the current output value, lengthens the next measuring duration in comparison with the current measuring duration, in particular by 5% to 20%.
11. Device (V) according to one of Claims 8 to 10, characterised in that the processing unit (VA) acquires a sensor-detected acceleration quantity, calculates a comparison speed value in dependence on the acceleration quantity and reduces the current output value, for example by 10%, if the last ascertained speed value is greater, for example by 10%, than the comparison speed value, or increases the curremt output value, for example by 10%, if the last ascertained speed value is less, for example by 10%, than the comparison speed value.
12. Device (V) according to one of Claims 8 to 11, characterised in that the processing unit (VA) sets a fixed minimum speed measuring duration, for example 3 seconds, im dependence om the last ascertained speed value and a fixed speed minimum value, im particular of 2.5 km/h, in the case where the last ascertained speed value lies below the fixed speed minimum value, and sets a fixed maximum speed measuring duration, for example 0.3 seconds, in dependence on the last ascertained speed value and a fixed speed maximum value, in particular of 25 km/h, in the case where the last ascertained speed value lies above the fixed speed maximum value.
13. Electric bicycle comprising a device, wherein the device is preferably a device according to one of Claims 8 to 12, suitable for generating an output value which represents a speed value, wherein the device is suitable for carrying out a method according to one of Claims 1 to 7.
14. A device for generating an output value which represents a speed value substantially as hereinbefore described with reference to the accompanying drawings.
15. A method for generating an output value which represents a speed value substamtially as hereinbefore described with reference to the aocompanyimg drawings.
16. An electric bicycle substantially as hereinbefore described with reference to the accompanyimg drawings.