DK178684B1

DK178684B1 - Electronic parking disc

Info

Publication number: DK178684B1
Application number: DKPA201670213A
Authority: DK
Inventors: Søren Andersen; Poul Dørup Olesen
Original assignee: S A Invest Aps
Priority date: 2016-04-08
Filing date: 2016-04-08
Publication date: 2016-11-07
Also published as: DK201670213A1

Abstract

An electronic parking disc (100) for a vehicle comprising a housing configured for mounting at a fixed position in the vehicle, and, contained within the housing an electronic timer (108), a motion sensor (106) for detecting spatial motion of the electronic parking disc, a control system (104), an electronic display (102), and a source (110) of electric power for powering the electronic components of the parking disc. The control system is configured to automatically assess changes of state of the vehicle from parked to driving, and from driving to parked, and to cause the display to indicate a point in time of commencement of parking of the vehicle upon assessment of a change of state from driving to parked. The change of state of the vehicle from parked to driving is determined when the time derivative exceeds a predetermined threshold value, and the change of state from driving to parked when the time derivative is smaller than a predetermined threshold value for a predetermined time interval.

Description

ELECTRONIC PARKING DISC Field of invention

The present invention relates to an electronic parking disc for a vehicle. The invention relates in particular to a parking disc based on a built-in motion sensor and associated control software for determining if the vehicle is in a driving or a parking state.

Background of the invention

Parking areas allowing for cost-free parking for a certain period of time, such as one hour, are common and generally appreciated by motorists. In order for parking attendants to establish the point in time of commencement of parking of a vehicle, drivers utilizing such parking areas are normally required to place a parking disc behind the vehicle's windscreen in such a manner that a display indicating the exact or approximate time of commencement of parking is visible from the outside. Manually operable parking discs have been known for decades. These typically comprise a planar sheet of plastics or cardboard, to which a manually rotatable arrow is mounted, allowing the driver to place the arrow in a position relative to a clock face printed on the planar sheet. Alternatively, a separate clock face leaf may be rotatably mounted to the planer sheet, allowing the driver to set the time of commencement of parking by adequate rotation of the clock leaf.

It is well known that parking tickets are frequently written to motorists having forgotten to set their manually operable parking disc, or in case such parking disc has been erroneously set to indicate a time of commencement of parking not matching the true time of parking commencement. In order to protect motorists from such unfortunate occurrences, which are often perceived as instances of injustice, electronic parking discs have been developed with a view to always and automatically set a clock display upon parking of the vehicle. With a view to allowing the parking disc to operate in parking garages or other areas in which GPS connectivity is obstructed, and to provide parking discs which are easy to install and inexpensive in manufacture, parking discs have been proposed which rely on built-in-motion sensors for assessing if the vehicle is in a parked or driving state.

Various examples of electronic parking discs comprising such motion sensors are known from EP-A-1 221 676, EP-A-1 231 572, WO-A-2004/114225, and WO-A-2010/131059. While such parking discs have been well received by users, it has been found that some commercially available electronic parking discs with built-in motion sensors either suffer from an undesirably long latency time when their state is to change from parked to driving, or from driving to parked, or that they are over-sensitive, thus misinterpreting minor movements caused by, e.g., manual rocking of a parked car as driving motion and inferring a risk of fraudulent use of the parking disc.

Description of the invention

On the above background, it is an object of embodiments of the invention to provide an electronic parking disc with a built-in motion sensor which is reliable, inexpensive, and which builds on available standard components. In particular, it is an object of embodiments of the invention to provide a parking disc which avoids undesirably long latency time in change of state, and which is yet reliable in the sense that the risk of fraudulent use should be avoided or at least minimized.

According to a first aspect, the invention provides an electronic parking disc for a vehicle comprising a housing configured for mounting at a fixed position in the vehicle, and, contained within the housing: an electronic timer; a motion sensor for detecting spatial motion of the electronic parking disc; a control system operatively connected to the timer and the motion sensor, the control system being configured to receive respective output signals of the timer and the motion sensor; an electronic display operatively connected to the control system and the timer; a source of electric power for powering the timer, the control system and the electronic display; wherein the control system is configured to: assess, on the basis of the output signals of the timer and the motion sensor, changes of state of the vehicle from parked to driving, and from driving to parked; cause the display to indicate a point in time of commencement of parking of the vehicle upon assessment of a change of state from driving to parked; switch off the display or otherwise cause the display to indicate a driving state of the vehicle upon assessment of a change of state from parked to driving; and wherein the control system is configured to determine a time derivative of the output signal of the motion sensor and to assess a change of state of the vehicle from parked to driving when the time derivative exceeds a predetermined threshold value; or assess a change of state of the vehicle from driving to parked when the time derivative is smaller than a predetermined threshold value for a predetermined time interval.

It has been found that changes of state of the vehicle can be reliably detected without non-acceptably long latency times on the basis of the time derivative of the output signal of the motion sensor. This is due to the fact that changes of a time derivative of a motion indicator, notably the time derivative of acceleration, beyond an appropriately set threshold value are unavoidable under real driving conditions and yet difficult if not impossible to achieve in attempted fraudulent use by non-driving impacts to the vehicle, such as rocking of a parked car.

The motion sensor may comprise any device or system for detecting motion, including one or more sensors which rely on external data communication, such as a GPS system, or one or more sensors which operate independently from external data connections, i.e. which produce an output signal solely on the basis of a mechanical or electro-mechanical impact, or on the basis of optical detection. Exemplary embodiments of sensors which operate independently from external data communication include gyroscopes, accelerometers, optical motion detection systems for detecting motion by vision, or any combination thereof. Sensors operating on the basis of mechanical or electro-mechanical input may, e.g., be based on piezoelectric sensor elements.

To enhance reliability of the motion sensor, it may comprise a multiple-axes accelerometer in order to allow detection of motion to be based on the combined input of a time derivative of acceleration in at least two directions. The directions of the multiple-axes accelerometer may be mutually orthogonal or at any other angle relative to one another. By use of a multiple-axes accelerometer, the risk of a change of state being erroneously detected on the basis of pure vertical or pure transverse acceleration is eliminated, and risks of fraudulently caused changes of state are thus reduced.

In order to reduce latency time and increase reliability, the assessment of a change of state of the vehicle from driving to parked or from parked to driving is preferably based on the absolute value (i.e. the modulus, also referred to as the numerical value) of the time derivative of the output signal of the motion sensor. Thus, in the control system, the sign of any negative value of the derivative is switched, whereby the negative derivative is treated as a positive one of the same magnitude.

In one embodiment, the control system is configured to sample the output signals of the motion sensor at discrete time intervals and to determine the time derivative of the output signal of the motion sensor on the basis of at least two mean values of samplings at discrete time intervals of the output signals of the motion sensor. For example, each of the mean values may be based on 10 to 100 samplings obtained at a frequency of, e.g. 10 to 20 samplings per second. Instances of errors due to signal noise or accidental or unusual motion are preferably avoided by calculation of the time derivative on the basis of mean values. In one particularly preferred embodiment, the control system is configured to omit an extreme upper sampled value and/or an extreme lower sampled value from a calculation of each of the mean values. Whereas such upper and/or lower extreme values may represent true motion as it occurs in reality, experience has shown that extremes may be caused by signal noise or other errors not reflecting physical reality. In another embodiment, extremes deviating by more than a certain percentage from the mean values may be omitted from calculation of the mean value. Such procedure, however, requires more computer power than a plain discarding of the upper and/or lower extremes, which may therefore be preferred.

In embodiments of the invention, in which the accelerometer comprises a multiple-axes accelerometer, the control system may be configured to sample the output signals of the accelerometer of at least two of the axes of the accelerometer and to obtain the time derivatives thereof individually in respect of each of the axes of the accelerometer. Changes of state of the vehicle may thus be assessed when at least one or at least two of the time derivatives exceeds the predetermined threshold value. As mentioned above, the risk of errors and risks of fraud are thereby reduced. The multiple-axes accelerometer may be a two- or three-axes accelerometer with mutually orthogonal axes. In the case of an xy- or xyz-accelerometer, mounting thereof in a windshield forming an acute angle relative to vertical does not result in errors when at least two axes are applied in the control system's signal processing, inasmuch as acceleration in the driving direction of the vehicle inevitably results in simultaneous acceleration along at least two axes under real driving conditions.

The control system is preferably configured to assess the change of state of the vehicle from parked to driving when each of a plurality of successively determined time derivative values exceeds the predetermined threshold value. Thus, a single value exceeding the threshold will not lead to a change of state. Reliability is thus enhanced, and the risk of fraud is further reduced.

In order to further reduce the risk of fraud, the timer, motion sensor, control system and display may be protected from exterior manipulation, including mechanical, electrical and programmable manipulation. The computer code of the control system is thus preferably stored in a non-accessible executable format only on a non-interchangeable chip. The timer, sensor and CPU of the control system are preferably non-releasably secured to, e.g., a circuit board.

The electric power source may comprise a solar cell power system, which may preferably be embedded within the housing, a battery which may likewise be embedded in the housing, and/or an interface for an external voltage source, such as a low-voltage circuit of the vehicle.

Brief description of the drawings

Embodiments of the invention will now be further described with references to the drawings, in which:

Fig. 1 illustrates an embodiment of an electronic parking disc according to the invention;

Fig. 2 is an acceleration chart of an exemplary operating condition of a vehicle;

Fig. 3 is a velocity chart of the operating condition forming the basis of Fig. 2;

Fig. 4 shows the time derivative corresponding to the acceleration chart of Fig. 2;

Fig. 5 is a flow chart illustrating operation of a control system of an embodiment of the parking disc according to the invention.

Detailed description of the drawings

The parking disc 100 illustrated in Fig. 1 comprises a housing 101 and, contained within the housing, a clock display 102 for displaying, in a parked state of the vehicle, the exact or approximate time of commencement of parking, such as, e.g. the quarter hour immediately following commencement of parking. In the driving state of the vehicle, the display 102 is either switched off, caused to show the actual time, or caused to otherwise indicate a driving state of the vehicle. The display 102 is controlled by a control system 104 comprising a CPU for processing output signals of a motion sensor embodied as an accelerometer 106, and a timer 108. The clock display 102, control CPU 104, timer 108 and optionally motion sensor 106 are powered by a built-in battery 112, which in turn is charged by a solar cell system 110 with solar cells exposed on the exterior surface of the housing. The solar cell system 110 renders exchange of the battery 112 superfluous, or at least extends intervals between battery exchange. In alternative embodiments, the parking disc does not comprise the solar cell system 110, in which case the battery may replaceable. In a yet further alternative embodiment, the parking disc may comprise an interface for powering thereof by means of an external voltage supply, such as an ignition or voltage system of the vehicle.

Fig. 2 is an acceleration chart of an exemplary operating condition of a vehicle. At commencement of operation and until time tif acceleration of the vehicle increases linearly.

From time tx until t2, acceleration is constant, and from t2 until t3, acceleration decreases to zero. From t3 until t4, acceleration is zero. From t4 until t5, acceleration decreases linearly until a constant negative acceleration is reached, which remains constant between t5 and t6, and finally acceleration increases to zero from t6 until t7. In a preferred embodiment of the invention, the motion sensor comprises an accelerometer, and the chart depicted in Fig. 2 thus represents the output signal produced by the motion sensor, albeit sampled at discrete time intervals.

Fig. 3 is a velocity chart of the operating condition forming the basis of Fig. 2. At commencement of operation and until time ti, acceleration of the vehicle increases linearly and velocity thus increases exponentially. From time ti until t2, acceleration is constant and velocity thus increases linearly. From t2 until t3, acceleration decreases linearly to zero, whereby velocity continues to increase. Acceleration is zero between t3 and L,, and thus velocity is constant. As acceleration decreases linearly from t4 until t5, velocity drops exponentially, and at constant negative acceleration between t5 and t6, velocity decreases linearly. As acceleration increases back to zero from t6 until t7, velocity decreases further to zero.

Fig. 4 shows the time derivative corresponding to the acceleration chart of Fig. 2. At commencement of operation until tlf the time derivative is positive. From ^ until t2, the derivative of acceleration is zero. Between t2 and t3, the derivative is negative, and between t3 and it is zero. The derivative is zero again between and t5, zero from t5 until t6 and positive between t6 and t7.

According to the present invention, in embodiments in which the motion sensor comprises an accelerometer, the time derivative of acceleration as depicted in Fig. 4 forms the basis of the control system's determination of the state of the vehicle. In a preferred embodiment of the invention, the absolute values of the time derivatives form the basis of the control system's determination of the state of the vehicle. Thus, in the example of Figs. 2-4, the sign of the negative values of derivatives of acceleration occurring between t2 and t3, and between t4 and t5, is switched from minus to plus, whereby the negative values are treated as positive values of the same magnitude.

Fig. 5 is a flow chart illustrating operation of a control system of an embodiment of a parking disc according to the invention.

It should be understood that the detailed description and specific examples, whilst indicating embodiments of the invention, are given by way of illustration only. Various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the present disclosure.

Claims

An electronic parking disc for a vehicle comprising a housing, said parking disc adapted to be mounted at a fixed position in the vehicle and, contained within the housing: an electronic timer; a motion sensor for detecting spatial movement of the electronic parking disk; a control system operatively connected to the timer and the motion sensor, the control system being adapted to receive respective output signals from the timer and the motion sensor; an electronic display operatively connected to the control system and the timer; an electrical power source to supply the timer, control system and electronic display with power; wherein the control system is adapted to: - evaluate, based on the output signals of the timer and motion sensor, changes in the state of the vehicle from parked to driving, and from driving to parked; - cause the display to indicate a time for parking of the vehicle after assessing a change in condition from driving to parked; switch off the display or otherwise cause the display to indicate a running state of the vehicle after assessing a change in state from parked to driving; characterized in that the control system is adapted to determine a time derivative of the motion sensor output signal and to - assess a change in the state of the vehicle from parked to driving when the time derivative exceeds a predetermined threshold; or - assess a change in vehicle condition from driving to parked when the time derivative is less than a predetermined threshold in a predetermined time interval.

An electronic parking disc according to claim 1, wherein the motion sensor comprises an accelerometer.

An electronic parking disc according to claim 2, wherein the accelerometer comprises a multi-axis accelerometer.

An electronic parking disc according to any one of the preceding claims, wherein the assessment of a change in the state of the vehicle from driving to parked or from parked to driving is based on the absolute value of the time derivative of the motion sensor's output signal.

An electronic parking disk according to any one of the preceding claims, wherein the control system is arranged to: sample the motion signals output signals at discrete time intervals; and determining the time derivative of the motion sensor output signals based on at least two averages of samples at discrete time intervals of the motion sensor output signals.

An electronic parking disc according to claim 5, wherein the control system is adapted to omit an extreme upper sampled value and an extreme lower sampled value from a calculation of each of the mean values.

An electronic parking disc according to claim 5 or 6, wherein the accelerometer comprises a multi-axis accelerometer and wherein the control system is arranged to: sample the accelerometer output signals for at least two of the accelerometer axes and obtain the time derivatives thereof individually for each of the the axes of the accelerometer; and - assessing the changes in the state of the vehicle when at least one of the time derivatives exceeds the predetermined threshold.

An electronic parking disc according to any one of claims 5-7, wherein the control system is adapted to assess the change in the vehicle state from parked to driving when each of a plurality of successively determined time-derived values exceeds the predetermined threshold value.

An electronic parking disc according to any of the preceding claims, wherein the timer, motion sensor, control system and display are protected from outside manipulation.

An electronic parking disk according to any one of the preceding claims, wherein the electrical energy source comprises a solar energy system, a battery, and / or an external voltage source interface.