DEVICE AND METHOD FOR DETERMINING THE SPEED OF AT LEAST ONE WHEEL OF A VEHICLE

Description

[0001] The present invention relates to a device for determining a rotational speed of at least one wheel of a vehicle and to a corresponding method.

[0002] In highly automated driving, for example, a vehicle driver does not need to be permanently seated in a driver's seat and available for corrective intervention. Therefore, conventional fallback systems for critical situations cannot be used. If a primary braking system is unavailable, a redundant braking system should take over the driver's role. To be able to replicate ABS functionality in a redundant situation, for example, both braking systems are conventionally supposed to read signals from wheel speed sensors.

[0003] DE 10 2016 222 628 A1 discloses a sensor arrangement comprising a sensor, a first and a second evaluation unit, each with a measuring resistor, a first and a second voltage source connected to the first and second evaluation units, respectively, and switching means designed as diode-Zener diode combinations and connected to the sensor.

[0004] Against this background, it is the object of the present invention to provide an improved device for determining a rotational speed of at least one wheel of a vehicle and an improved method for determining a rotational speed of at least one wheel of a vehicle.

[0005] This object is achieved by a device for determining a rotational speed of at least one wheel of a vehicle and by a method for determining a rotational speed of at least one wheel of a vehicle according to the main claims.

[0006] According to embodiments, in particular, a sensor signal from an active speed sensor can be redundantly read in, used, and additionally or alternatively evaluated to determine a speed of a wheel of a vehicle. For this purpose, the sensor signal can be tapped by a first control unit and a second control unit. In the event of a malfunction of one of the control units, the sensor signal can be tapped by the functioning control unit. Thus, the sensor signal can be tapped or read in, used, and additionally or alternatively evaluated by at least one control unit.

[0007] Advantageously, according to embodiments, redundancy with respect to a speed sensor can be achieved, particularly in a space-saving manner, without duplicating the sensor. Thus, redundant use of an active speed sensor can also be achieved cost-effectively, since each additional sensor would entail additional costs. For example, ABS functionality can be easily implemented for redundantly designed brake systems. Thus, costs and installation space can be saved through the redundant use of a single speed sensor.

[0008] A device for determining a rotational speed of at least one wheel of a vehicle is presented, the device having the following features: a detection device for detecting an angular velocity of the wheel that is correlated with the rotational speed, wherein the detection device is designed to provide an electrical detection signal depending on the detected angular velocity; a first control unit with a first measuring device for measuring the detection signal, wherein the first control unit is electrically connected to the detection device; and a second control unit with a second measuring device for measuring the detection signal, wherein the second control unit is electrically connected to the detection device, wherein the detection device is electrically switchable or switched between the first measuring device and the second measuring device.

[0009] The vehicle may be a commercial vehicle, such as a truck or the like. The control units may be microcontrollers or the like. The detection device may function as a controlled current source. The electrical detection signal may be a current signal. Measuring the detection signal may mean determining a signal characteristic or property of the detection signal. Electrically connected may mean a connection via electrical conductors.

[0010] According to the invention, the first control unit has at least one first switching device, which is designed to interrupt a transmission of the detection signal between the first measuring device and the detection device in the event of a malfunction of the first control unit. The second control unit has at least one second switching device, which is designed to interrupt a transmission of the detection signal between the second measuring device and the detection device in the event of a malfunction of the second control unit. A malfunction can represent a failure of a component or power supply of a control unit. In a state without electrical power, each switching device can assume an open position in which an electrical current flow is interrupted.Such an embodiment offers the advantage that the detection signal can be used in a simple and reliable manner by only faultlessly functioning control devices.

[0011] The first measuring device is electrically connected between a first switching device and the detection device. The second measuring device is electrically connected between a second switching device and the detection device. Such an embodiment offers the advantage that the use of the detection signal by at least one control unit can be enabled reliably and cost-effectively.

[0012] Furthermore, the detection device can be configured to provide the detection signal with electrical current level sequences dependent on the angular velocity. Such an embodiment offers the advantage of enabling a reliable and accurate determination of the rotational speed.

[0013] The first control unit can also be part of a first redundancy level of a vehicle's braking system. The second control unit can be part of a second redundancy level of the vehicle's braking system. Each redundancy level can have at least its own power supply and its own control unit. Such an embodiment offers the advantage that the detection signal can be used directly by components already provided. This also allows the device to be implemented cost-effectively and in a space-saving manner.

[0014] According to the invention, the first measuring device has a first electrical current measuring resistor and a first evaluation device for evaluating a voltage drop across the first current measuring resistor. The second measuring device has a second electrical current measuring resistor and a second evaluation device for evaluating a voltage drop across the second current measuring resistor. Such an embodiment offers the advantage that the rotational speed can be determined redundantly in a simple and accurate manner. The second evaluation device can be electrically connected in parallel to the second current measuring resistor. The first measuring device can have a differential measuring value amplifier that is electrically connected in parallel to the first current measuring resistor. The first evaluation device can be connected to the measuring value amplifier. The measuring value amplifier can be an operational amplifier.Such an embodiment offers the advantage that an uncomplicated and exact determination of the speed can be made possible in a redundant manner.

[0015] The first control unit also has a first high-side switch, a first low-side switch, a first electrical voltage source, and a first ground connection. The first voltage source and the first ground connection are electrically connected between the first high-side switch and the first low-side switch. The first current measuring resistor is electrically connected between the first high-side switch and the detection device. The second control unit has a second high-side switch, a second low-side switch, a second electrical voltage source, and a second ground connection. The second voltage source and the second ground connection are electrically connected between the second high-side switch and the second low-side switch. The second current measuring resistor is electrically connected between the second low-side switch and the detection device.Such an embodiment offers the advantage that the detection signal can be used by at least one faultlessly functioning control unit in a cost-effective and space-saving manner in order to realize a redundant determination of the rotational speed.

[0016] Here, the first control unit can have an additional first current measuring resistor, which is electrically connected between the first voltage source and the first low-side switch, or between the first low-side switch and the detection device. The second control unit can have an additional second current measuring resistor, which is electrically connected between the detection device and the second high-side switch, or between the second high-side switch and the second voltage source. Each additional current measuring resistor can be assigned an additional evaluation device. Such an embodiment offers the advantage that the measurement of the detection signal can be even more precise and reliable.

[0017] A method for determining a rotational speed of at least one wheel of a vehicle is also presented, wherein the method is carried out using an embodiment of the above-mentioned device. The method comprises the following steps: Detecting the rotational speed-correlated angular velocity of the wheel using the detection device to provide an electrical detection signal dependent on the detected angular velocity; and measuring the detection signal using the first controller when the first controller is operating correctly, using the second controller when the second controller is operating correctly, and using the first controller and the second controller when the first controller and the second controller are operating correctly, to determine the rotational speed.

[0018] This allows the detection signal to be used by both control units if both control units are functioning correctly, and by one of the control units functioning correctly in the event of a malfunction or failure of one of the control units, in order to be able to determine the speed redundantly in a simple and reliable manner.

[0019] Examples of the approach presented here are explained in more detail in the following description with reference to the figures. They show: Fig. 1 a schematic representation of a vehicle with a device according to an embodiment; Fig. 2 a schematic representation of a device according to an embodiment; and Fig. 3 a flowchart of a method for determining according to an embodiment.

[0020] Fig. 1 shows a schematic representation of a vehicle 100 with a device 110 for determining according to an exemplary embodiment. The vehicle 100 is a motor vehicle, for example a commercial vehicle, in particular a truck or the like. The vehicle 100 has a plurality of wheels 102. In the representation of Fig. 1 For reasons of clarity, only one wheel 102 is explicitly designated as an example. The wheel 102 can rotate at an angular velocity Ω, which is correlated with a rotational speed of the wheel 102.

[0021] The vehicle 100 has the device 110 for determining, or a determining device 110. The determining device 110 is designed to determine the rotational speed of the wheel 102 or multiple wheels 102 of the vehicle 100. According to the exemplary embodiment illustrated here, the determining device 110 has a detection device 120, a first control unit 130, and a second control unit 140. The detection device 120 is illustrated here only for one wheel, although those skilled in the art will recognize that a detection device 120 should be provided for each of the wheels 102.

[0022] The detection device 120 is designed to detect the angular velocity Ω of the wheel 102, which is correlated with the rotational speed of the wheel 102. In this case, the detection device 120 is assigned at least to the wheel 102. According to one exemplary embodiment, the detection device 120 can also have a plurality of sensor elements that can be assigned to a plurality of wheels 102 of the vehicle 100. Alternatively, the determination device 110 can have a plurality of detection devices 120 (one on each wheel) for a plurality of wheels 102 of the vehicle 100. The detection device 120 is designed to provide an electrical detection signal 125 depending on the detected angular velocity Ω. The detection signal 125 can have electrical current level sequences I(Ω) or level sequences of an electrical current that are dependent on the angular velocity Ω. The detection device 120 can also be referred to as an angular velocity sensor 120.

[0023] The detection device 120 is electrically connected to the first control unit 130 and to the second control unit 140. Thus, the first control unit 130 and the second control unit 140 are also connected to the detection device 120 in a signal-transmitting manner. The first control unit 130 has a first measuring device 132 for measuring the detection signal 125. The second control unit 140 has a second measuring device 142 for measuring the detection signal 125. The detection device 120 is electrically connected between the first measuring device 132 and the second measuring device 142. More precisely, the first control unit 130 and the second control unit 140 are connected to one another by means of two electrical lines, with the detection device 120 being electrically connected to both electrical lines. A first of the electrical lines is connected to the first measuring device 132.A second of the electrical lines is connected to the second measuring device 142.

[0024] According to one embodiment, the vehicle 100 has a braking system 104 with a first level and a redundancy level, wherein the braking system 104 can also be used in the Fig. 1 may include sensors not shown. Here, the first control unit 130 is part of the first level of the braking system 104 or is assigned thereto, wherein the second control unit 140 is part of the redundancy level of the braking system 104 or is assigned thereto.

[0025] The determination device 110 is also referred to with reference to Fig. 2 discussed in more detail below.

[0026] Fig. 2 shows a schematic representation of a device 110 for determining or determining device 110 according to an embodiment. The determining device 110 corresponds or is similar to the determining device from Fig. 1 . More specifically, the determination device 110 corresponds to the determination device of Fig. 1 , wherein the determining device 110 in the illustration of Fig. 2 is merely presented in more detail.

[0027] According to the exemplary embodiment illustrated here, the first control unit 130 has a first electrical current measuring resistor 231, a first evaluation device 233, a differential measuring amplifier 234, a first high-side switch 235, a first low-side switch 236, a first electrical voltage source 237, and a first ground connection 238. Strictly speaking, the differential measuring amplifier 234 illustrated here is an operational amplifier which serves as a current mirror to relate the measured value to GND. Here, the first electrical current measuring resistor 231, the first evaluation device 233, and the differential measuring amplifier 234 are parts of the first measuring device 132. In other words, the first measuring device 132 has the first electrical current measuring resistor 231, the first evaluation device 233, and the differential measuring amplifier 234.

[0028] The first evaluation device 233 is configured to evaluate a voltage drop across the first current measuring resistor 231. The measuring amplifier 234 is electrically connected in parallel with the first current measuring resistor 231. The first evaluation device 233 is connected to the measuring amplifier 234. The measuring amplifier 234 is connected to an electrical supply voltage Vs. For example, the first evaluation device 233 operates according to the so-called AK protocol of the automotive industry working group or a similar protocol based on a controlled current source.

[0029] The first voltage source 237 and the first ground connection 238 are electrically connected between the first high-side switch 235 and the first low-side switch 236. The first voltage source 237 is designed, merely by way of example, to provide an electrical voltage of 12 volts. The first current measuring resistor 231 is electrically connected between the first high-side switch 235 and the detection device 120. Thus, the first measuring device 132 is electrically connected between the first high-side switch 235 and the detection device 120. The first high-side switch 235 and the first low-side switch 236 represent first switching devices. Each of the first switching devices is designed to interrupt a transmission or a transmission path of the detection signal between the first measuring device 132 and the detection device 120 in the event of a malfunction of the first control unit 130.

[0030] According to the exemplary embodiment illustrated here, the second control unit 140 has a second electrical current measuring resistor 241, a second evaluation device 243, a second high-side switch 245, a second low-side switch 246, a second electrical voltage source 247, and a second ground connection 248. The second electrical current measuring resistor 241 and the second evaluation device 243 are parts of the second measuring device 142. In other words, the second measuring device 142 has the second electrical current measuring resistor 241 and the second evaluation device 243.

[0031] The second evaluation device 243 is configured to evaluate a voltage drop across the second current measuring resistor 241. For this purpose, the second evaluation device 243 is electrically connected in parallel with the second current measuring resistor 241. The second evaluation device 243 operates, for example, according to the so-called AK protocol of the automotive industry working group or a similar protocol based on a controlled current source.

[0032] The second voltage source 247 and the second ground terminal 248 are electrically connected between the second high-side switch 245 and the second low-side switch 246. The second voltage source 247 is designed, merely by way of example, to provide an electrical voltage of 12 volts. The second current measuring resistor 241 is electrically connected between the second low-side switch 246 and the detection device 120. Thus, the second measuring device 142 is electrically connected between the second low-side switch 246 and the detection device 120. The second high-side switch 245 and the second low-side switch 246 represent second switching devices. Each of the second switching devices is designed to interrupt a transmission or a transmission path of the detection signal between the second measuring device 142 and the detection device 120 in the event of a malfunction of the second control unit 140.

[0033] According to one embodiment, the first control unit 130 may have an additional first current measuring resistor or a first low-side current measuring resistor, which may be electrically connected between the first voltage source 237 and the first low-side switch 236 or between the first low-side switch 236 and the detection device 120. The second control unit 140 may have an additional second current measuring resistor or a second high-side current measuring resistor, which may be electrically connected between the detection device 120 and the second high-side switch 245 or between the second high-side switch 245 and the second voltage source 247.

[0034] The measuring device presented here can also be arranged (on both sides) between the voltage source and the switch.

[0035] Fig. 3shows a flowchart of a method 300 for determining according to an exemplary embodiment. The method 300 for determining can be executed to determine a rotational speed of at least one wheel of a vehicle. In this case, the method 300 for determining can be executed using, by means of, or in conjunction with the device from one of the figures described above or a similar device.

[0036] In a detection step 310, in the method 300 for determining, the angular velocity of the wheel, which correlates with the rotational speed, is detected using the detection device of the device in order to provide the electrical detection signal depending on the detected angular velocity. For this purpose, the detection device is suitably controlled using a control signal. Subsequently, in a measuring step 320, the detection signal is measured in order to determine the rotational speed. In this case, the measuring step 320 is carried out using at least one of the control units. More specifically, the measuring step 320 is carried out using all of the control units that exhibit fault-free operation.In particular, the measuring step 320 is performed using the first controller when the first controller is operating correctly, using the second controller when the second controller is operating correctly, and using the first controller and the second controller when the first controller and the second controller are operating correctly.

[0037] In other words, and with reference to the figures described above, the detection device 120, which can also be referred to as a sensor, can be viewed as a controlled current source. The detection device 120 outputs specific current level sequences as the detection signal 125, depending on the angular velocity Ω of the wheel 102. For detection, the electrical current or the detection signal 125 is passed through the current measuring resistors 231 and 241, and the voltage drop is determined. The active speed sensor 120 or the detection device 120 can be used twice by using current measuring resistors 231 and 241 or shunts, one per control unit, in a series circuit. The high-side current measuring resistor or the first current measuring resistor 231 of the first control unit 130 additionally uses the differential measuring amplifier 234.

[0038] If the first control unit 130 and the second control unit 140 are both functioning correctly, the first high-side switch 235 and the second low-side switch 246 are closed, while the first low-side switch 236 and the second high-side switch 245 are open. In such an operating state of the determination device 110, electrical current flows from the first control unit 130 via the first high-side switch 235, the first current measuring resistor 231, the detection device 120, the second current measuring resistor 241, and finally via the second low-side switch 246 to the second ground connection 248. If one of the control units 130 and 140 fails, supply and measurement can also occur independently. In this case, the switches in the faulty control unit are open, and the switches in the faultlessly functioning control unit are closed.

[0039] Alternatively, a switch arrangement can be used as a switch. Ground offsets can affect the body diode of MOSFETs. Therefore, in practice, two MOSFETs are often used in series. This also results in new possible positions for the shunt.

[0040] Ground offsets, which can be caused by line resistances of supply lines and by different current draws of control units 130 and 140, lead to a variable operating voltage of the detection device 120. If the detection device 120 operates in a voltage range of 8 to 20 volts, the ground offset can be limited to a maximum of 4 volts, for example, whereby this value depends on the supply voltage. In this specific case, the mean value of the sensor operating voltage is (8 V + 20 V) / 2 = 14 V, and the distance at 14 V to the edge is 14 V - 8 V ​​= 6 V. LIST OF REFERENCE SYMBOLS

[0041] 100Vehicle 102Wheel 104Braking system 110Device or determination device 120Detection device 125Detection signal 130First control unit 132First measuring device 140Second control unit 142Second measuring device ΩAngular velocity 231First electrical current measuring resistor 233First evaluation device 234Differential measuring amplifier 235First high-side switch 236First low-side switch 237First electrical voltage source 238First ground connection 241Second electrical current measuring resistor 243Second evaluation device 245Second high-side switch 246Second low-side switch 247Second electrical voltage source 248Second ground connection VsSupply voltage 300Method for determining 310Detection step 320Step of measuring

Claims

1. An apparatus (110) for determining a rotational speed of at least one wheel (102) of a vehicle (100), wherein the apparatus (110) has the following features: a detection device (120) for detecting an angular velocity (Ω) of the wheel (102) that is correlated to the rotational speed, wherein the detection device (120) is designed to provide an electrical detection signal (125) depending on the angular velocity (Ω) detected; a first control unit (130) with a first measurement device (132; 231, 233, 234) for measuring the detection signal (125), wherein the first control unit (130) is electrically joined to the detection device (120), wherein the first control unit (130) comprises at least one first switching device (235, 236) that is designed to interrupt a transmission of the detection signal (125) between the first measurement device (132; 231, 233, 234) and the detection device (120) in the event of a malfunction of the first control unit (130), wherein the first measurement device (132; 231, 233, 234) comprises a first electrical current measurement resistor (231) and a first evaluation device (233) for evaluating a voltage drop across the first current measurement resistor (231), wherein the first control unit (130) comprises a first high-side switch (235), a first low-side switch (236), a first electrical voltage source (237) and a first ground terminal (238), wherein the first voltage source (237) and the first ground terminal (238) are electrically connected between the first high-side switch (235) and the first low-side switch (236), wherein the first current measurement resistor (231) is electrically connected between the first high side switch (235) and the detection device (120), and a second control unit (140) with a second measurement device (142; 241, 243) for measuring the detection signal (125), wherein the second control unit (140) is electrically joined to the detection device (120), wherein the detection device (120) can be electrically switched or is electrically switched between the first measurement device (132; 231, 233, 234) and the second measurement device (142; 241, 243), wherein the second control unit (140) comprises at least one second switching device (245, 246) that is designed to interrupt a transmission of the detection signal (125) between the second measurement device (142; 241, 243) and the detection device (120) in the event of a malfunction of the second control unit (140), wherein the second measurement device (142; 241, 243) comprises a second electrical current measurement resistor (241) and a second evaluation device (243) for evaluating a voltage drop across the second current measurement resistor (241), wherein the second control unit (140) comprises a second high-side switch (245), a second low-side switch (246), a second electrical voltage source (247) and a second ground terminal (248), wherein the second voltage source (247) and the second ground terminal (248) are electrically connected between the second high-side switch (245) and the second low-side switch (246), wherein the second current measurement resistor (241) is electrically connected between the second low-side switch (246) and the detection device (120), wherein the first measurement device (132; 231, 233, 234) is electrically connected between a first switching device (235, 236) and the detection device (120), wherein the second measurement device (142; 241, 243) is electrically connected between a second switching device (245, 246) and the detection device (120).

2. The apparatus (110) as claimed in claim 1, characterized in that the detection device (120) is designed to provide the detection signal (125) with electrical current level sequences that depend on the angular velocity (Ω).

3. The apparatus (110) as claimed in one of the preceding claims, characterized in that the first control unit (130) is part of a first redundancy level of a braking system (104) of the vehicle (100), wherein the second control unit (140) is part of a second redundancy level of the braking system (104) of the vehicle (100).

4. The apparatus (110) as claimed in one of the preceding claims, characterized in that the second evaluation device (243) is electrically connected in parallel with the second current measurement resistor (241), wherein the first measurement device (132; 231, 233, 234) comprises a differential instrumentation amplifier (234) that is electrically connected in parallel with the first current measurement resistor (231), wherein the first evaluation device (233) is connected to the instrumentation amplifier (234).

5. The apparatus (110) as claimed in one of the preceding claims, characterized in that the first control unit (130) comprises an additional first current measurement resistor that is electrically connected between the first voltage source (237) and the first low-side switch (236) or between the first low-side switch (236) and the detection device (120), wherein the second control unit (140) comprises an additional second current measurement resistor that is electrically connected between the detection device (120) and the second high-side switch (245) or between the second high-side switch (245) and the second voltage source (247).

6. A method (300) for determining a rotational speed of at least one wheel (102) of a vehicle (100), wherein the method (300) can be carried out making use of the apparatus (110) as claimed in one of the preceding claims, wherein the method (300) comprises the following steps: detecting (310) the angular velocity (Ω) of the wheel (102) that is correlated to the rotational speed making use of the detection device (120) to provide an electrical detection signal (125) depending on the angular velocity (Ω) detected; and measuring (320) the detection signal (125) making use of the first control unit (130) when the first control unit (130) is operating without fault, making use of the second control unit (140) when the second control unit (140) is operating without fault, and making use of the first control unit (130) and the second control unit (140) when the first control unit (130) and the second control unit (140) are operating without fault in order to determine the rotational speed.