SE1150074A1 - Method for determining a braking position for a regenerative braking of a vehicle, device, braking system and vehicle - Google Patents

Abstract

A method for determination of a braking location for regenerative braking of a vehicle (1) to a known stop location. The regenerative braking is effected with a braking force which comprises a regenerative force component Fe imparted by a regenerative brake system (30) of the vehicle. The method comprises the steps of: i) determining a distance between a momentary location and the stop location, ii) determining a braking distance for said regenerative braking on the basis of the momentary speed and Fe ,iii) determining whether the distance between the momentary location of the vehicle and the stop location is within said braking distance, and iv) generating a signal that said braking location has been reached if the distance between the momentary location of the vehicle and the stop location is within said braking distance, otherwise the above method steps are repeated.

Description

For example, regenerative braking is used in vehicles such as cars, trains, trucks, etc., comprising an electric motor adapted to use electrical energy during acceleration and to regeneratively reuse the vehicle's kinetic energy when braking the vehicle. The electric motor thus has both the function of an electric motor and an electric generator. Even in hybrid vehicles comprising two or more motors powered by different energy sources, there are usually means for regenerative braking, such as one or more electric motors.

Since the means for regenerative braking is only capable of delivering braking power up to a maximum, the vehicle also includes a non-regenerative means for braking the vehicle, such as wheel brakes, and so on. A braking system of the vehicle comprising the regenerative braking means and the non-regenerative braking means is adapted to provide a composite braking force.

A problem with vehicles according to the state of the art is that a driver of the vehicle without assistance has difficulty braking the vehicle optimally with regard to the recovery of kinetic energy and temporal progress. If the braking distance for braking the vehicle to the stop position is shorter than what the means for regenerative braking can provide, energy will be lost in the means for non-regenerative braking. The wear on the means for non-regenerative braking will also increase in comparison if the braking was only performed by means of the means for regenerative braking. Conversely, if the braking distance for braking the vehicle to the stop position is longer than what the means for regenerative braking needs for regenerative braking, the braking of the vehicle will require a longer time than necessary. In addition, it is desirable to brake the vehicle with a braking force that is less than a certain level in order to allow comfort to the driver and any passengers. As a result, the braking of the vehicle takes place in a non-optimal manner with respect to time, which means that the traffic rhythm and / or timetable are negatively affected.

GB2460528 A shows a system for regenerative braking of an electric vehicle. The regenerative braking begins when the vehicle passes over a coil. A problem with the system is that the braking takes place between predetermined braking and stopping positions.

US2010 / OO42304 A1 discloses a method for controlling the power flow in a vehicle on the basis of the probability of a deceleration during the progress of the vehicle.

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for solving the problems of the prior art. A first object of the invention is a method for assisting the driver in braking the vehicle by means of a regenerative braking.

A second object of the invention is to support the driver so that the braking of a vehicle takes place optimally with regard to the recovery of kinetic energy, temporal progress and comfort.

The invention also relates to a device according to claim 13 for carrying out the method, a braking system according to claim 14 and a vehicle according to claim 15.

These objects are achieved by the initially stated method characterized by the steps: - receiving information about an instantaneous position, a momentary speed and said known stopping position of the vehicle, - determining a distance between the instantaneous position of the vehicle and the stopping position on the basis of the instantaneous position and the stopping position, - determining a braking distance for said regenerative braking of the vehicle to said stopping position on the basis of the instantaneous speed and Fe, - determining the distance between the instantaneous position of the vehicle and the stopping position is within said braking distance, and - generating a signal indicating that said braking position has been reached if the distance between the instantaneous position of the vehicle and the stopping position is within said braking distance, otherwise repeating the above method steps.

The distance between the instantaneous position of the vehicle and the stop position is determined, for example, on the basis of the coordinates of the instantaneous position and the stop position, as well as a determined length scale between the coordinates.

The information about the instantaneous position of the vehicle is generated by a position system. The vehicle's stop position is given by stop positions along the vehicle's travel route that are either predetermined or generated during the vehicle's travel. The instantaneous speed of the vehicle is given by a speed sensor of the vehicle. The braking distance of the vehicle depends on the instantaneous speed and Fe.

By indicating to the driver when the distance between the vehicle's instantaneous position and the stop position is within braking distance for the regenerative braking, the driver is assisted in driving the vehicle optimally with regard to recovery of kinetic energy and temporal progress. This gives the driver information about the braking position when the regenerative braking of the vehicle is to be initiated in order for the optimal regenerative braking.

According to an embodiment of the invention, the length of said braking distance is determined mainly on the basis of the magnitude of Fe and the instantaneous speed of the vehicle. In this way, the braking distance is optimized with regard to the recovery of the kinetic energy, whereby otherwise influencing parameters during braking are given secondary importance. According to an embodiment of the invention, the method comprises applying said braking position so that the braking distance for the regenerative braking is minimized. This indicates the braking position so that as short a braking distance as possible is achieved, which is advantageous with regard to the vehicle's progress.

According to an embodiment of the invention, the determination of said braking position takes place dynamically by applying the braking distance on the basis of the instantaneous speed of the vehicle. By dynamic setting of the brake position is meant that the brake position is determined continuously while driving the vehicle. Thus, the braking position is not a fixed point along the vehicle's travel route.

According to an embodiment of the invention, the method comprises increasing the braking distance by a distance corresponding to a reaction distance with which the vehicle travels during a reaction time for performing the braking up to the braking position.

By extending the braking distance by the distance with which the vehicle travels during a reaction time for carrying out the braking, it is ensured that braking is not started too late to take place on the basis of Fe.

According to an embodiment of the invention, the method comprises: - receiving the signal indicating that said braking position has been reached by a braking system which induces said regenerative braking with Fe.

The regenerative deceleration is started upon receipt of the signal indicating that said braking position has been reached.

Thereby an automatic braking of the vehicle takes place as soon as the braking position for regenerative braking to the stop position has been reached. According to an embodiment of the invention, the driver is given the options to refuse or confirm the proposed automatic braking. According to an embodiment of the invention, the braking is performed on the basis of a further force component, Fr, which is created by an interaction between the environment and the vehicle, the determination of the braking distance also taking place on the basis of Fr.

Fr depends on the interaction between the environment and the vehicle, such as the braking force from the road slope, rolling resistance, air resistance, driveline losses, and so on. When braking in a downhill slope with respect to the vehicle's direction of travel to the stop position, the braking distance becomes shorter in comparison without a road slope. Conversely, when braking in the middle slope with respect to the vehicle's direction of travel to the stop position, the braking distance becomes longer in comparison without a road slope. Depending on the circumstances in the surroundings, the braking distance can thus be both extended and shortened when Fr.

According to an embodiment of the invention, the method comprises a determination of Fr with respect to the time, Fr (t), wherein the determination of the braking distance takes place on the basis of Fr (t).

According to an embodiment of the invention, the method comprises a determination of Fe with respect to the time, Fe (t), wherein the determination of the braking distance takes place on the basis of Fe (t).

Fe (t) depends on the properties of the regenerative agent. For example, the regenerative agent allows different Fe for different speeds of the vehicle, the determination of Fe (t) depending on the instantaneous speed of the vehicle.

According to an embodiment of the invention, the method comprises the use of a plurality of stop positions which are predetermined along a travel route of the vehicle. Stop positions are, for example, stops for the vehicle, such as a bus stop, unloading place, and so on.

According to an embodiment of the invention, the stop positions comprise stops along a travel route for the vehicle, the method comprising activating the stop positions while driving the vehicle. For example, the stop position is activated by a passenger on the vehicle or by a signal from a person at the stop position, or information is received about traffic lights, duty to stop, and so on.

According to an embodiment of the invention, the instantaneous position of the vehicle is determined by a GPS receiver. According to an embodiment of the invention, the instantaneous position of the vehicle is determined by receiving information from position markers along the vehicle's route or dead count from either a starting position and a position marker for the vehicle's travel.

According to an embodiment of the invention, determination of the braking distance for said regenerative braking of the vehicle to said stopping position is performed on the basis of a determined braking force.

This makes it possible to decelerate the vehicle so that a desired comfort is created.

According to an embodiment of the invention, the braking distance is determined on the basis of at least either a calculation process and tabulated values. According to one embodiment, the tabulated values are predetermined on the basis of a number of different instantaneous speeds for the vehicle and Fe, preferably also on the basis of Fr.

According to an embodiment of the invention, the braking distance is determined on the basis of an iterative calculation process comprising the following steps: - setting a counter, n to zero and a time parameter, tn, to zero at the time of receiving the instantaneous speed of the vehicle (1), a) determining a step length, T, for counting tn to a certain value, b) determining a partial distance, s (tn), during a time period from tn to the sum of tn and T on the basis of the expression s (tn ) = s (tn_1) + v (tn_1) * T + TZ / m (Fe (tn) + F, (tn)), where "n" and "n-1" are indices, and tn 10 15 20 25 30 Refers to the current time period and t ,, _ 1 refers to a possible previous time period, whereby the information about s (tn) is saved, where s (tn_1) indicates a time-dependent distance component, v (t ,, _ 1) indicates a time-dependent speed component, m indicates the mass of the vehicle (1), Fe (t ,,) indicates a time dependence of Fe and F, (t ,,) indicates a time dependence of Fr, c) initiation of a subsequent time period by counting n me d 1 and application of tr, to t + T, d) determination of a partial speed, v (tn), for the subsequent time period on the basis of the expression v (t ,,) = v (t ,, _ 1) + T / m (Fe (t ,,) + Ff (tn)), e) determining whether v (tn) in step d) for the following time period exceeds a certain value, f) Repeating steps a) -f) for the following time period the one with v (tn) if v (t ,,) in step d) exceeds the determined value, otherwise summing up s (tn) for the time periods and setting the braking distance to the sum of s (t ,,).

The iterative method steps determine the braking distance, which is then compared with the distance between the vehicle's instantaneous position and the stop position. The number of iterations depends on the T and the size of the vehicle's instantaneous speed.

According to an embodiment of the invention, the method comprises learning stop positions along an itinerary, which learned stop positions are adapted to be used in a subsequent journey along the itinerary. The learning takes place, for example, by saving stop positions when traveling along an itinerary, whereby the saved information about the stop positions is used for subsequent travel along the itinerary.

According to an embodiment of the invention, the stop positions include, for example, information on traffic lights, stop duty, etc. or information from an adaptive cruise control. According to an embodiment of the invention, the determination of the braking distance also depends on rolling resistance, kinetic energy, mass, expected road inclination, and so on.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in more detail by describing various embodiments of the invention and with reference to the accompanying drawings.

Figure 1 shows a driveline for a vehicle according to an embodiment of the invention.

Figure 2 shows a flow chart of a method for activating a regenerative braking of a vehicle according to the invention.

Figures 3a and 3b each show a flow chart of a method for determining the braking distance for regenerative braking of a vehicle according to an embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Figure 1 shows a driveline for a vehicle 1 which interacts with the method according to the invention.

The vehicle 1 comprises a first engine 3 and a second engine 5.

Preferably, the first motor 3 and the second motor 5 are operated with different energy sources. According to an embodiment of the invention, the first engine 3 is an internal combustion engine driven by, for example, petrol or diesel and the second engine an electric motor 5.

The vehicle 1 comprises a first energy storage 7, a second energy storage 9 and a generator 11. The first energy storage 7 is adapted to supply energy to the first engine 3. The first energy storage 7 is, for example, a fuel tank. The first motor 3 is connected to generator 11 which generates and charges the second energy storage 9 with electricity. The second energy storage 9 is, for example, an electric battery. In this case, a series hybrid is described, the invention can also be realized with a parallel hybrid or complex hybrid.

The vehicle 1 comprises a regenerative means 20 for braking the vehicle 1. In the embodiment shown, the regenerative means 20 is the same as the second engine 5. The regenerative means 20 is adapted to brake the vehicle 1 with a regenerative force component, Fe, while energy is converted to a form adapted to charge the second energy storage 9. Preferably, the regenerative means 20 is an electric motor which acts as a motor when the vehicle 1 is accelerated and as a generator when the vehicle 1 is regeneratively braked.

The vehicle 1 also comprises one or more non-regenerative means 22 for braking the vehicle 1 comprising a braking means which creates a braking action on the vehicle 1 during the development of heat. According to one embodiment, the non-regenerative means 22 for braking the vehicle 1 comprises wheel brakes of the vehicle 1. The vehicle 1 is adapted to be braked by both the regenerative means 20 and the non-regenerative means 22 for braking. Thereby, the vehicle 1 is adapted to provide a sufficient braking force for the braking, regardless of whether the regenerative means 20 is able to provide this braking force or not.

The vehicle 1 also comprises a braking system 30 for braking the vehicle 1. The braking system 30 comprises a device 40 for determining a brake position for regenerative braking of the vehicle 1. The device comprises calculating means 42, such as a logic unit, a computer processor, etc., which is adapted receiving information for the determination of the braking position and performing the determination of the braking position. The braking system includes, for example, different types of known braking systems, which may be provided with anti-spin, ABS, etc. The device 40 comprises indicating means 44 adapted to create a signal indicating that the braking position for regenerative braking of the vehicle 1 has been reached. According to an embodiment of the invention, the device 40 is adapted to create a signal to the regenerative means 20 which starts the regenerative braking of the vehicle 1 with Fe.

Figure 2 shows a flow chart of a method for activating a regenerative braking of a vehicle 1 according to the invention.

The method is adapted to be performed regularly, for example 10 times per second.

The method begins with a step 210 in which information is received about an instantaneous speed and position of the vehicle 1, and a stop position to which the vehicle 1 is desired to be decelerated. Then, in a step 220, a determination of the distance between the instantaneous position and the stop position is performed.

The instantaneous position of the vehicle 1 is preferably received from a positioning system, such as a GPS receiver.

The instantaneous speed of the vehicle 1 is received from a speed sensor, such as a permanently mounted speed sensor in the vehicle.

According to an embodiment of the invention, the stop position of the vehicle 1 is determined by stop points predetermined along the route, such as stops, unloading points, stop signs, and so on. According to another embodiment of the invention, the stop position of the vehicle 1 is determined by activating the stop position during the travel of the vehicle, for example with a passenger creating a stop signal or receiving information about traffic lights, stop duty, etc. According to another embodiment of the invention, the information on stop positions for the vehicle 1 is created by means of a traffic flow system, where stop positions along the route are continuously determined. In a step 240, the braking distance of the regenerative deceleration to the stop position is determined on the basis of the instantaneous speed of the vehicle 1, Fe (tn), Fr (tn) and the mass of the vehicle 1, m.

According to an embodiment of the invention, the braking distance is extended by a distance corresponding to a distance that the vehicle 1 has time to travel during a characteristic reaction time before the driver has time to start the regenerative braking.

After determining the distance between the instantaneous position and the stop position and after determining the braking distance, it is examined in a step 250 whether the vehicle 1 is within the braking distance for the regenerative braking of the vehicle 1.

If the vehicle 1 is not within the braking distance, the previously described method steps 210 to 240 are repeated. The method is repeated continuously during the operation of the vehicle 1 until the vehicle 1 is within the braking distance for the regenerative braking.

If, on the other hand, the vehicle 1 is within the braking distance, a signal is generated in a step 260 which indicates to the driver to initiate the regenerative braking of the vehicle 1 to the stop position. After generating the signal, the method is restarted from the beginning.

According to an embodiment of the invention, the signal causes the braking system 30 to initiate the regenerative braking of the vehicle 1. Thus, the braking of the vehicle 1 takes place in an automatic manner.

According to an embodiment of the invention, the braking distance is determined by an iterative calculation according to one of Figs. 3a and 3b. According to another embodiment of the invention, the determination takes place on the basis of tabulated values. The tabulated values are determined on the basis of a number of different instantaneous speeds for the vehicle and Fe, preferably also on the basis of Fr. The tabulated values are, for example, stored in a database, which enables a quick determination of the braking distance. By using tabulated values, the process load is reduced in comparison with whether the determination takes place through the iterative calculation.

Figures 3a and 3b each show a flow chart of a method for determining the braking distance for regenerative braking of a vehicle 1 according to an embodiment of the invention.

In a step 310, a counter, n, is set to zero and a time parameter, tn, is set to zero upon receiving the instantaneous speed information.

In a step 320, a step length, T, is set to a certain value.

The step length is used to calculate tn during the determination of the braking distance.

In relation to the use of a large step length, a small step length gives an accurate determination at the expense of many iteration steps. Conversely, a large step length requires a smaller number of iterations compared to when using a small step length but at the expense of a lower accuracy in determining the braking distance. Thus, the step length should be adapted to the speed at which the computing means 42 is able to perform the iteration steps.

In a step 325, a determination of the time dependence of Fe, Fe (t ,,) is performed. Fe (tn) depends mainly on the instantaneous speed of the vehicle 1.

In a step 330, a determination of a partial distance, s (t ,,) is performed for each time period below tn to tn + T. The determination is performed on the basis of the expression: Sun) = S (tn-1) + V (tn-1) * T + TZ / m (Fe (tn) + Frun »- 10 15 20 25 30 14 In a step 340 after the determination of s (t), a subsequent time period is initiated by counting n by 1 and assigning tn to tn + T. Before starting the following time period, in a step 350 a partial speed, v (tn), is determined for the following time period based on the expression: Van) = V (tn-1) + T / m (Feun) + Frun »- l a step 360 examines whether v (tn) for the subsequent time period exceeds a certain value. If v (tn) for the subsequent time period exceeds the determined value, the method is repeated from step 320 on the basis of v (tn) for the subsequent time period.

If, on the other hand, v (tn) for the subsequent time period is equal to or less than the determined value, s (tn) is summed for the time periods and the braking distance is set to the sum of s (tn) in a step 370. Thereafter, the iterative calculation method is repeated.

In Fig. 3b, in a step 322, a determination of the time dependence of Fr, Fr (tn) is also performed. The determination of Fr (tn) takes place on the basis of an interaction between the environment and the vehicle. For example, Fr (tn) depends on ambient conditions, such as road slope, turning radius, rolling resistance, air resistance, and on the instantaneous speed of the vehicle 1.

The calculation method for the regenerative deceleration is based on the following physical relationships: To solve the above physical relationships, the equations must be discretized, for example by using the Euler method backwards, which gives the expression according to claim 12 steps b) and d).

The invention is not limited to the embodiments shown but can be modified and varied within the scope of the appended claims.

Claims (15)

10 15 20 25 30 35 16 REQUIREMENTS A method of determining a braking position for a regenerative braking of a vehicle (1) to a known stopping position, said regenerative braking taking place with a braking force comprising a regenerative force component, Fe, created by a regenerative braking system ( 30) of the vehicle (1), characterized in that the method comprises the steps of: - receiving information about an instantaneous position, a instantaneous speed and said known stopping position of the vehicle (1), - determining a distance between the instantaneous of the vehicle (1) position and the stop position on the basis of the instantaneous position and the stop position, - determining a braking distance for said regenerative braking of the vehicle (1) to said stop position on the basis of the instantaneous speed and Fe, - determining whether the distance between the vehicle ( 1) the instantaneous position and the stop position are within said braking distance, and - generating a signal indicating that said braking position has been reached if the distance me The instantaneous position of the vehicle (1) and the stop position are within said braking distance, otherwise repeating the above method steps. The method according to claim 1, wherein the determination of the length of said braking distance is mainly based on the magnitude of Fe and the instantaneous speed of the vehicle (1). The method according to any one of claims 1 or 2, wherein the method comprises applying said braking position so that the braking distance for the regenerative braking is minimized. The method according to any one of the preceding claims, wherein the determination of said braking position takes place dynamically by applying the braking distance on the basis of the instantaneous speed of the vehicle (1). The method according to any of the preceding claims, wherein the method comprises increasing the braking distance by a distance corresponding to an estimated reaction distance with which the vehicle (1) travels during a reaction time for performing the braking up to the braking position. The method according to any one of the preceding claims, wherein the method comprises: - receiving the signal indicating that said braking position has been reached by a braking system (30) which induces said regenerative braking with Fe. The method according to any of the preceding claims, wherein the braking is performed on the basis of an additional force component, Fr, which is created by an interaction between the environment and the vehicle (1), wherein the determination of the braking distance also takes place on the basis of Fr. The method according to any one of the preceding claims, wherein the method comprises arranging at least one additional stop position along a travel route of the vehicle (1). The method of claim 8, wherein said at least one further stop position comprises a stop along a travel route of the vehicle (1), the method comprising activating the stop positions while driving the vehicle (1). The method according to any one of the preceding claims, comprising determining the instantaneous position of the vehicle (1) by means of a GPS receiver. 10 15 20 25 30 35 18 The method according to any of the preceding claims, wherein the determination of the braking distance is based on at least one of a calculation process and tabulated values. The method according to any of the preceding claims, wherein the determination of the braking distance takes place on the basis of an iterative calculation process comprising the following steps: - setting of a counter, n to zero and a time parameter, tn, to zero at the time of reception of the instantaneous speed of the vehicle (1), a) setting a step length, T, for counting tn to a certain value, b) determining a partial distance, s (t ,,), during a time period from tn to the sum of tr, and T on the basis of the expression s (t ,,) = s (t ,, _ 1) + v (t ,, _ 1) * T + TZ / m (Fe (tn) + F, (t ,,)) , where "n" and "n-1" are indices, and tn refers to the current time period and t ,, _ 1 refers to a possible preceding time period, whereby the information about s (t ,,) is saved, where s (t ,,) _1) indicates a time-dependent distance component, v (t ,, _ 1) indicates a time-dependent speed component, m indicates the mass of the vehicle (1), Fe (tn) indicates a time-dependent of Fe and Fr (t ,,) indicates a time-dependent of Fr, c ) initiation of a subsequent time period by enumeration of n with 1 and application of tr, to tn + T, d) determination of a partial speed, v (tn), for the subsequent time period on the basis of the expression v (tn) = v (t ,, _ 1) + T / m (Fe (tn) + Ff (tn)), e) determining whether v (tn) in step d) for the subsequent time period exceeds a certain value, f) Repeating steps a) -f) for the subsequent time period with v (t ,,) if v (t ,,) in step d) exceeds the determined value, otherwise summing s (tn) for the time periods and applying the braking distance to the sum of s (t ,,). A device (40) for determining a brake position by the method according to any one of claims 1-12, characterized in that the device (40) comprises calculating means (42) adapted to receive information for determining the brake position and indicating means. (44) adapted to create a signal indicating that said braking position has been reached. A brake system (30) for regenerative braking from a brake position, characterized in that the brake system (30) comprises the device (40) according to claim 13 and means (30) for regenerative braking which are adapted to induce a regenerative braking of the vehicle (1). A vehicle adapted to be braked regeneratively, characterized in that the vehicle (1) comprises one of the device (40) according to claim 13 and the braking system (30) according to claim 14.