The present invention relates to a vehicle weight calculation apparatus, a bumpy road and a vehicle weight calculation method capable of calculating a weight of a vehicle (hereinafter referred to as “vehicle weight”).
Among conventional vehicle weight calculation apparatuses, there is one that estimates a weight of a vehicle being driven on a road with varying inclination and generates estimate values of the vehicle weight through a recursive process using data including variables indicating the vehicle speed and a longitudinal force acting on the vehicle, and a statistical filter using statistical representation of an inclination of the road (e.g., PTL 1).
PTL 1
Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-500525
However, since the technique described in PTL 1 uses the statistical filter, it involves a large calculation load for calculating estimate values of the vehicle weight and involves large errors in the estimate values of the vehicle weight.
An object of the present invention is to provide a vehicle weight calculation apparatus, a bumpy road and a vehicle weight calculation method that are capable of reducing the calculation load for calculating a vehicle weight without using any statistical filter and calculating the vehicle weight with fewer errors.
The present invention provides a vehicle weight calculation apparatus that calculates a weight of a vehicle, including: a storage section that stores position information in association with an angular frequency of a bumpy road; and a control section that calculates the weight of the vehicle, in which: the control section calculates the weight of the vehicle based on acceleration of the vehicle in a vertical direction and the angular frequency of the bumpy road corresponding to a current position of the vehicle stored in the storage section.
The present invention provides a bumpy road formed to calculate a weight of a vehicle, in which the bumpy road is formed so as to be displaced at a predetermined angular frequency in a vertical direction of the vehicle.
The present invention provides a vehicle weight calculation method for calculating a weight of a vehicle, the method including calculating the weight of the vehicle based on acceleration of the vehicle in a vertical direction and an angular frequency of a bumpy road corresponding to a current position of the vehicle.
According to the present invention, the weight of the vehicle is calculated based on acceleration in the vertical direction of the vehicle and an angular frequency of a bumpy road corresponding to a current position of the vehicle stored in the storage section, which provides effects of calculating the vehicle weight without use of any statistical filter, reducing the calculation load in calculating the vehicle weight and enabling calculation of the vehicle weight with fewer errors.
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Among all the drawings provided for describing the embodiment, the same elements are assigned the same reference numerals in principle and duplicate description thereof will be omitted.
Each component of an embodiment of the present invention will be described with reference to
Vehicle weight calculation apparatus 10 is mounted on vehicle 1 and has a function of calculating a weight of vehicle 1 itself (vehicle weight). A road on which vehicle 1 runs is formed in advance as a bumpy road which is displaced at a predetermined angular frequency in a vertical direction of the vehicle. The term “bumpy” here refers to a sine wave shape. When vehicle 1 is running on this bumpy road, vehicle weight calculation apparatus 10 detects acceleration in the vertical direction of vehicle 1 and calculates the weight of vehicle 1 based on the angular frequency of the bumpy road and the detected acceleration.
More specifically, vehicle weight calculation apparatus 10 is provided with a storage section 105 that stores position information in association with the angular frequency of the bumpy road and control section 101 that calculates the weight of the vehicle, and control section 101 calculates the weight of vehicle 1 based on the acceleration in the vertical direction of vehicle 1 and the angular frequency of the bumpy road corresponding to the current position of vehicle 1 stored in storage section 105. Hereinafter, each section will be described in detail.
Control section 101 controls each section which will be described later, receives detection results of the sections and calculates the weight of vehicle 1.
GPS receiver 102 receives signals from a plurality of GPS (Global Positioning System) satellites, demodulates the received signals and can thereby acquire the current position of vehicle 1. The acquired current position of vehicle 1 is outputted to control section 101. That is, GPS receiver 102 corresponds to a current position acquiring section.
Wheel speed sensor 103 is a sensor that can detect a minute amount of rotation of a tire of vehicle 1 and outputs, for example, one detection pulse for every predetermined amount of rotation. Control section 101 can calculate the amount of travel of vehicle 1 by measuring the detection pulses outputted from wheel speed sensor 103. This amount of travel is as small as 4 centimeters, for example.
As shown in
Storage section 105 is a storage medium such as a flash memory or hard disk. Storage section 105 stores information (hereinafter referred to as “road surface angular frequency information R) including position information of vehicle 1 associated with the angular frequency of the bumpy road. The position information is information on, for example, one latitude and longitude at which the bumpy road is located.
The angular frequency of the bumpy road is an angular frequency corresponding to displacement of the bumpy road in the vertical direction. The angular frequency of the bumpy road varies depending on the actual running speed of vehicle 1. A “direct distance on the road corresponding to one cycle of a sine shape” can be stored in storage section 105 as an “angular frequency of the bumpy road.” In this way, control section 101 can calculate the angular frequency of the bumpy road if the actual running speed of vehicle 1 can be acquired.
In addition, an “angular frequency at a predetermined speed” can alternatively be stored as an “angular frequency of the bumpy road.” Control section 101 can calculate the angular frequency of the bumpy road from a ratio between the predetermined speed and the actual running speed. That is, the “angular frequency of the bumpy road” may be a value which can be calculated from the actual running speed of vehicle 1.
The bumpy road formed to calculate the weight of the vehicle is formed at a predetermined position in advance. When calculating the vehicle weight using the angular frequency of the bumpy road, control section 101 needs to obtain the angular frequency of the bumpy road on which vehicle 1 is currently running Thus, storage section 105 stores information including position information of vehicle 1 associated with the angular frequency of the bumpy road.
As will be described later, storage section 105 also stores spring modulus k when a vibration model of vehicle 1 is modelled using a spring having spring modulus k. Storage section 105 also stores a maximum weight value of vehicle 1.
Announcement section 106 announces various kinds of information to occupants of vehicle 1 using sound information (speech, music or the like) or optical information (screen representation, blinking or the like, and is controlled by control section 101. More specifically, announcement section 106 is constructed of a speaker, display, LED or the like.
For example, when vehicle 1 is overloaded, announcement section 106 announces the overload to the occupants. Storage section 105 further stores a maximum weight of vehicle 1 and when the calculated weight of vehicle 1 is equal to or greater than the maximum weight of vehicle 1 stored in storage section 105, control section 101 controls announcement section 106 so as to announce the overload.
Communication section 107 is operated when vehicle 1 sends/receives various kinds of information to/from communication equipment (not shown) outside vehicle 1 and is controlled by control section 101. Communication section 107 can employ various communication schemes such as DSRC (Dedicated Short Range Communication).
<Operation of Vehicle Weight Calculation Apparatus 10>
Operation of vehicle weight calculation apparatus 10 according to the embodiment of the present invention will be described with reference to
Control section 101 first acquires the current position from the output of GPS receiver 102 of vehicle 1 (S01) and determines whether or not storage section 105 stores road surface angular frequency information R corresponding to the current position (S02). When road surface angular frequency information R is not stored (NO in S02), control section 101 ends the process.
When storage section 105 stores road surface angular frequency information R (YES in S02), control section 101 acquires vertical direction acceleration Az from the output of three-axis acceleration sensor 104 (S03). Acquired vertical direction acceleration Az together with position information of the current position is stored in storage section 105.
Next, the current position is acquired again (S04), and it is determined whether or not road surface angular frequency information R is stored (S05). When storage section 105 stores road surface angular frequency information R (YES in S05), S03 is executed again.
When storage section 105 does not store road surface angular frequency information R (NO in S05), control section 101 performs a process of calculating weight m of vehicle 1 based on the position information stored in S03 and vertical direction acceleration Az (S06). Details of the process in S06 will be described later.
After calculating weight m of vehicle 1, control section 101 determines whether or not the vehicle is overloaded (S07). Control section 101 reads a maximum weight of vehicle 1 from storage section 105 and when calculated weight m of vehicle 1 is equal to or greater than the maximum weight, control section 101 determines that the vehicle is overloaded. When the vehicle is overloaded (YES in S07), control section 101 controls announcement section 106 so as to announce that the vehicle is overloaded using sound information or optical information. When the vehicle is not overloaded (NO in S07), control section 101 ends the process.
Next, an example of the process of calculating vehicle weight m shown in S06 in
As shown in
The model shown in
According to Hooke's law, natural angular frequency ωk of the model in
Natural angular frequency ωk=√(spring modulus k/vehicle weight m) (Equation 1)
Equation 1 can be transformed into:
Vehicle weight m=spring modulus k/(natural angular frequency ωk)̂2 (Equation 2)
Spring modulus k is a value specific to vehicle 1 and is stored in storage section 105 in advance. That is, if natural angular frequency ωk is calculated, vehicle weight m can be calculated.
The running of vehicle 1 on the bumpy road displaced at a predetermined angular frequency in the vertical direction is equivalent to forcibly vibrating the springs with spring modulus k shown in
An equation of motion when displacement of combined spring 23 is X and a sine-function-like external force is added is:
Vehicle weight m*X″=spring modulus k+S*sin(ωt) (Equation 3)
where S is an amplitude of an external force given from the bumpy road.
The form of the solution to the equation of motion of forced vibration expressed by (Equation 3), in which attenuation by friction, air resistance and the like are not considered is:
X=(S/m)/(ωk̂2−ω̂2)*sin(ωt) (Equation 4)
When acceleration of X is calculated from equation 4,
X″=(S/m)*(ω̂2)/(ω̂2−ωk̂2)*sin(ωt) (Equation 5)
It can be understood by equation 5 that the acceleration (vertical direction acceleration Az) becomes a maximum (infinite) when ω coincides with natural angular frequency ωk. In reality, however, due to various attenuation factors, Az never becomes infinite even if ω coincides with natural angular frequency ωk.
Next, the formation of the bumpy road will be described. As shown in
The bumpy road is divided into a plurality of sections as shown in
As shown in
Next, a method of calculating natural angular frequency ωk from the angular frequency of the bumpy road with reference to
Regarding ωa to cod shown in
The relationship between the angular frequency and acceleration of the bumpy road is represented by a waveform in which acceleration becomes a maximum at natural angular frequency ωk as shown in
Natural angular frequency ωk varies depending on weight m of vehicle 1. As shown in
In the case of
Thus, by dividing the bumpy road into a plurality of sections and forming the sections so as to be displaced at a plurality of frequencies differing from one section to another, it is possible to estimate natural angular frequency ωk with a small calculation load. If natural angular frequency ωk can be calculated, it is possible to calculate weight m of vehicle 1 as shown in above equation 2.
The present embodiment calculates the weight of vehicle 1 based on the acceleration of vehicle 1 in the vertical direction detected by three-axis acceleration sensor 104 and the angular frequency of the bumpy road corresponding to the current position of vehicle 1 stored in storage section 105, and can thereby provide effects of calculating the vehicle weight without use of any statistical filter, reducing a calculation load of calculating the vehicle weight and enabling calculation of the vehicle weight with fewer errors.
<Variations>
Although the present embodiment has modelled a vibration model of the vehicle using one-degree-of-freedom system, but the vibration model is not limited to this. For example, the vibration model may be modelled in a two-degree-of-freedom system in which tires and suspensions are assumed to be separate springs. In addition, the vibration model may be modelled in a four-degree-of-freedom system in which front wheel and back wheel tires and suspensions are assumed to be separate springs.
In S01 and S04 in
The acquisition of the current position of vehicle 1 in S01 and S04 in
A case has been described in the present embodiment where vehicle weight calculation apparatus 10 mounted on vehicle 1 calculates a vehicle weight, but communication section 107 may transmit position information of vehicle 1 and acquired vertical direction acceleration Az so that the vehicle weight may be calculated outside vehicle 1.
A case has been described where when vehicle 1 is overloaded, announcement section 106 mounted on vehicle 1 announces the overload (S08 in
Road surface angular frequency information R stored in storage section 105 may be stored in advance before vehicle 1 starts running or may be received via communication section 107 and stored during running.
The present embodiment has illustrated announcement of overload as an application of calculation results of vehicle weight m, but there can be a variety of applications in addition to such an application.
In the foregoing embodiments, the present invention is configured with hardware by way of example, but the invention may also be provided by software in cooperation with hardware. The functional blocks used in the descriptions of the embodiments are typically implemented as LSI devices, which are integrated circuits. The functional blocks may be formed as individual chips, or a part or all of the functional blocks may be integrated into a single chip. The term “LSI” is used herein, but the terms “IC,” “system LSI,” “super LSI” or “ultra LSI” may be used as well depending on the level of integration.
In addition, the circuit integration is not limited to LSI and may be achieved by dedicated circuitry or a general-purpose processor other than an LSI. After fabrication of LSI, a field programmable gate array (FPGA), which is programmable, or a reconfigurable processor which allows reconfiguration of connections and settings of circuit cells in LSI may be used.
Should a circuit integration technology replacing LSI appear as a result of advancements in semiconductor technology or other technologies derived from the technology, the functional blocks could be integrated using such a technology. Another possibility is the application of biotechnology and/or the like.
The disclosure of the specification, drawings and abstract in Japanese Patent Application No. 2012-170782 filed on Aug. 1, 2012 is incorporated herein by reference in its entirety.
The vehicle weight calculation apparatus and the vehicle weight calculation method according to the present invention are suitable for use in a vehicle or the like whose weight needs to be calculated.
Number | Date | Country | Kind |
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2012-170782 | Aug 2012 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2013/004199 | 7/5/2013 | WO | 00 |