Method and control unit for operating a steering unit for a utility vehicle

Abstract

The invention relates to a method (400) for operating a steering unit (150) for a utility vehicle (100), said method comprising the following steps: starting the steering unit (150) if a driver (105) has not specified a steering request and if a vehicle speed (v) of the utility vehicle (100) is less than a predefined threshold value; if so, a controller unit 145 of a steering unit 150 of the commercial vehicle 100 is switched 410 into an inactive operating mode or the controller unit is operated in an inactive operating mode. Furthermore, the method 400 comprises the step of activating 420 a controller unit 145 of the steering unit 150 into an activated operating mode if it is detected that the driver 105 specifies a steering request or if a vehicle speed v of the commercial vehicle 100 exceeds the predefined threshold value.

Description

Technical Field

[0001] The invention relates to a method and a control unit for operating a steering unit for a commercial vehicle. Background Art

[0002] In commercial vehicles, hydraulic steering units are usually used to support the steering function in order to convert the driver's steering request into a specific deflection of the wheel. Here, a position regulator or sensor is usually used, which converts the position or deflection of the steering column into a signal, which is converted into the desired steering torque according to the desired steering angle position on the steering column. However, due to interference or generally due to noise, even in the case of a stationary vehicle or lack of a driver's steering request, the sensor signal of such a sensor is output, which causes the corresponding regulator unit of the steering unit to continuously try to compensate for the signal fluctuations caused by interference or noise. This in turn leads to the continuous active operation of the regulator unit, so that on the one hand, the regulator unit itself and on the other hand, the hydraulic pump controlled by the regulator unit consume energy unnecessarily. In addition, the hydraulic oil delivered by the hydraulic pump is unnecessarily heated, especially due to the wheels that are not moved and therefore can hardly be steered, so that the wheels wear out earlier on the one hand, and on the other hand, due to overheating, functional failures of the steering unit may occur. Summary of the invention

[0003] Against this background, the object of the present approach is to provide an improved method for operating a steering unit for a commercial vehicle, an improved control unit for operating a steering unit for a commercial vehicle, and an improved commercial vehicle.

[0004] The concept proposed here implements a method for operating a steering unit for a commercial vehicle, wherein the method comprises the following steps:

[0005] - switching a control unit of a steering unit of the commercial vehicle into an inactive operating mode or operating the control unit in an inactive operating mode if it is detected that the driver has not given a steering request and if the vehicle speed of the commercial vehicle is less than a predefined threshold value; and

[0006] If a steering request specified by the driver is detected or if the vehicle speed of the commercial vehicle exceeds a predefined threshold value, the controller unit of the steering unit is activated into an active operating mode.

[0007] In the present case, a commercial vehicle can be understood as a vehicle for transporting goods or multiple people or a vehicle for completing work, in particular a truck, a bus or generally a work machine, such as a tractor or a combine harvester or similar machinery. In the present case, a steering unit can be understood as a unit that can receive a manual steering input from a driver of a commercial vehicle, for example, through a steering wheel, can mechanically, hydraulically or electrically enhance the manual steering input, and can output the manual steering input to a motion unit so as to deflect the wheels of the commercial vehicle to a desired steering angle. In the present case, a regulator unit can be understood as a unit that can read an input signal in the form of a physical variable, which represents the manual steering input of the driver and can provide a control signal for the motion unit as an output signal. For example, the steering input can be realized by turning the steering wheel, so that the physical variable can be read as a rotation angle of the steering wheel or a torque introduced on the steering wheel. Here, the regulator unit can be realized or implemented as a PID regulator, for example.

[0008] The approach proposed here is based on the recognition that steering control of a commercial vehicle is generally not necessary if, on the one hand, the vehicle is stationary or is traveling only at very low speeds and, on the other hand, no active steering input by the driver is detected. In this case, it can be assumed that signal fluctuations of the signal of the sensor that is to detect the driver's steering input are caused by noise or other interference, so that a control of these signal fluctuations is not relevant to the driving operation of the commercial vehicle and can therefore be omitted.

[0009] The solution proposed here is advantageous in particular in that, on the one hand, unnecessary energy expenditure for unnecessary steering adjustments can be avoided and, on the other hand, the steering unit has less wear and increased functional safety.

[0010] According to a special embodiment of the proposed solution, in the activation step, the controller unit can be activated in a delayed manner and / or by means of a weighted, in particular time-weighted, controller output signal. For example, the output signal of the controller unit can be weighted by means of a factor, for example a factor that is variable in time, so that a gentle and continuous control of the moving element can be achieved for steering the wheels of the commercial vehicle. Such an embodiment offers the advantage that high pressure fluctuations in the hydraulic circuit of the steering unit are avoided and unnecessary wear of the steering unit is also reduced as a result.

[0011] Particularly advantageous are embodiments of the approach proposed here in which the controller output signal is weighted and / or delayed using a linear function, a quadratic function and / or an exponential function. Such an embodiment offers the advantage that it is technically simple to output a smoothed or continuous control signal to the determination unit without having to worry about unnecessary time delays when controlling the deflection of the wheel.

[0012] Furthermore, embodiments of the approach proposed here are conceivable in which, in the switching step or activation step, a value is used as a predefined threshold value for the vehicle speed, which represents the maximum walking speed, in particular a value of a maximum of 3 or 5 kilometers per hour. Such an embodiment of the approach proposed here offers the advantage that the steering unit remains activated even when the commercial vehicle is driving slowly, so that even during such slow driving, a steering intervention by the driver can be carried out in a timely manner.

[0013] Particularly advantageous is an embodiment of the solution proposed here in which a PID controller is controlled as a controller unit in the switching step and / or activation step. Advantageously, such an embodiment enables fast and precise control of the desired yaw angle of the wheel.

[0014] Furthermore, according to another embodiment of the solution proposed here, in the switching step and / or the activation step, the regulator unit can be controlled in such a way that the physical variable regulated by the regulator unit does not exceed and / or falls below a maximum value. For example, such a regulated physical variable can be the pressure of the hydraulic fluid of the steering unit or the speed of the pump of the steering unit. Such an embodiment offers the advantage that a sudden increase or decrease in the pressure of the hydraulic fluid in the steering unit and a resulting abrupt steering movement or steering wheel movement are avoided.

[0015] Furthermore, in the switching step and / or the activation step, the regulator unit of the hydraulic steering system can also be actuated, in particular the hydraulic pump of the hydraulic steering system can be actuated via the regulator unit. Such an embodiment offers the advantage that the components of the steering unit that are usually already present can be actuated in a technically simple and advantageous manner to achieve the above-mentioned tasks.

[0016] According to another embodiment of the proposed solution, the regulating unit can also be controlled in the step of switching the regulating unit of the steering unit of the commercial vehicle from the active operating mode to the inactive operating mode so that the pressure in the hydraulic circuit of the steering unit does not drop below a predefined gradient threshold value, and / or in the step of activating the regulating unit of the steering unit of the commercial vehicle from the inactive operating mode to the active operating mode so that the pressure increase in the hydraulic circuit of the steering unit does not exceed a predefined gradient threshold value. The gradient threshold value can be understood as a parameter that reflects the maximum (positive or negative) slope that the pressure in the hydraulic circuit of the steering unit should have. Such an embodiment offers the advantage that no pressure peaks are caused in the hydraulic system of the steering unit and thus wear of the steering unit and risks caused by sudden movements of components of the steering unit are minimized as much as possible.

[0017] Furthermore, according to another embodiment of the proposed solution, in the switching step, the controller unit of the steering unit can also be activated using a brake signal that represents an activation state of the handbrake or the parking brake. Such an embodiment offers the advantage that when the handbrake or the parking brake is activated, it can be expected that the vehicle does not need to perform a steering movement, so that the steering unit can also be brought into an inactive state when the handbrake or the parking brake is in such an activated state.

[0018] This method variant can be implemented, for example, in the form of software or hardware or in a hybrid form consisting of software and hardware, for example in a control unit.

[0019] In addition, the solution proposed here realizes a control unit, which is configured to perform, control or implement a variant of the method proposed here in a corresponding device. Through this embodiment variant of the present invention in the form of a control unit, the task on which the present invention is based can also be solved quickly and efficiently.

[0020] For this purpose, the control unit can have at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or actuator for reading a sensor signal from a sensor or for outputting a control signal to an actuator and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a microcontroller or the like, wherein the memory unit can be a flash memory or a magnetic memory unit. The communication interface can be configured to read or output data wirelessly and / or by wire, wherein a communication interface that can read or output wired data can, for example, read these data from a corresponding data transmission line electrically or optically or output these data to a corresponding data transmission line.

[0021] In the present case, the control unit can be understood as an electrical appliance that processes sensor signals and outputs control signals and / or data signals accordingly. The control unit can have an interface that can be constructed in hardware and / or in software. In the hardware-based construction scheme, the interface can be, for example, a part of a so-called system ASIC that includes the various functions of the control unit. However, it is also possible that the interface is an integrated circuit of its own or is at least partially composed of discrete structural elements. In the software-based construction, the interface can be, for example, a software module that coexists with other software modules on a microcontroller.

[0022] A computer program product or a computer program with a program code is also advantageous, which can be stored on a machine-readable carrier or storage medium, such as a semiconductor memory, a hard disk memory or an optical memory, and in particular when the program product or the program is executed on a computer or a device, the program code is used to execute, implement and / or control the steps of the method described in one of the preceding embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Advantageous embodiments are explained by way of example with reference to the following figures. The figures show:

[0024] Figure 1 A schematic diagram showing a commercial vehicle;

[0025] Figure 2 A schematic diagram showing a circuit diagram for implementing the approach proposed herein;

[0026] Figure 3 a graph showing an exemplary approach for weighting or delaying the activation or deactivation of a regulator unit; and

[0027] Figure 4A flow chart of a method for operating a steering unit for a commercial vehicle is shown. DETAILED DESCRIPTION

[0028] In the following description, identical or similarly acting elements are provided with identical or similar reference symbols, wherein a repeated description is omitted for the sake of clarity.

[0029] Figure 1 A schematic diagram of a commercial vehicle 100 is shown. The commercial vehicle 100 is controlled by a driver 105, for example, by means of a steering wheel 110. If the driver 105 turns the steering wheel 110 and thereby specifies a steering request, such a rotation or such a torque can be detected by a sensor 115 on the steering column and converted into a corresponding sensor signal 120, which is transmitted to a control unit 125. In addition, a motion signal 135 can be output by a motion sensor 130, which can detect the movement of the commercial vehicle 100 and which is in turn read by the control unit 125. If it is now recognized that the driver 105 has not specified a steering request via the steering wheel 110 and at the same time the vehicle speed v of the vehicle is less than a predefined threshold value, the control unit 125 can, for example, switch a controller unit 145 of a steering unit 150 into an inactive operating mode via a switch unit 140. If a steering request is then detected by the driver 105 or if the vehicle speed v of the commercial vehicle 100 exceeds a predefined threshold value, the controller unit 145 of the steering unit 150, for example, can be switched to an activated state or operating mode by means of the activation unit 155 of the control unit 125. It is also conceivable that a brake signal 156 of a handbrake 157 is taken into account in the switching unit 140 or in the activation unit 155 of the control unit 125, as will be described in more detail below.

[0030] In this case, the controller unit 145 can be designed as a PID controller without limiting the generality and can control, for example, a hydraulic pump 160 of the steering unit 150 based on the transmission signal 120. The pressure in the hydraulic circuit 165 can be adjusted in a controlled manner by the hydraulic pump 160, for example, so that, for example, the movement element 170, which is designed as a hydraulic motor, can cause a deflection of the wheels 175 of the commercial vehicle 100. In this way, the commercial vehicle 100 can be steered according to the driver's specifications.

[0031] As briefly described above, measurement errors or noise in the sensor signal 120 may cause the controller unit 145 in the prior art to continuously attempt to compensate for signal fluctuations in the transmission signal, for example. This may result in increased energy consumption due to the operation of the controller unit 145 and, for example, the operation of the hydraulic pump 160 or the movement element 165, as well as increased wear of components of the steering system 150 or impaired functional performance, for example, due to unnecessary increases in the pressure or temperature of the hydraulic fluid.

[0032] In order to solve this problem, the solution proposed here now proposes a significant improvement. In particular, it is assumed here that it is usually not necessary to steer the commercial vehicle if, firstly, the driver has not made a steering request and, secondly, the vehicle is also in a stationary position or has at least a very low vehicle speed. In this case, it can be assumed that the signal fluctuations in the sensor signal 120 are due to interference or noise, and therefore no active control of the steering movement by the control unit 145 is necessary. In this case, the control unit 145 can be switched to an inactive operating mode.

[0033] However, if either a steering request is made by the driver 105, for example by turning the steering wheel 110, or the vehicle is driven faster, for example faster than a threshold value of three or five kilometers per hour, it can be assumed that active steering of the vehicle is required and the regulator unit 145 should therefore be switched to the active operating mode. In this way, a quick response to a time-critical steering request by the driver 105 can be made.

[0034] Figure 2A schematic diagram of a circuit diagram for implementing the approach proposed here is shown. In this case, the control unit 125 comprises, for example, an UND coupling unit 200, a first input of which is connected to the output of a sensor signal comparator 210, and a second input of which is connected to the output of a motion signal comparator 220. In the sensor signal comparator 210, it is checked whether the sensor signal 120 is greater than a predetermined threshold value, which represents, for example, a limit value from which a torque actively applied by the driver to the steering wheel or a certain steering angle at which the driver turns the steering wheel is given. The motion signal comparator 220 determines whether the vehicle speed of the commercial vehicle 100 is greater than or equal to a predetermined threshold value, for example, greater than or equal to a walking speed of 3 to 5 kilometers per hour. If these two conditions are met, a deactivation signal (deactivation signal) is sent by the UND coupling unit 220 to the switching unit 140, which is designed to switch the regulator unit 145 to an inactive state, i.e., the regulator unit 140 does not perform regulation. However, if one of the conditions at the input of the UND coupling unit is not met, the activation unit 155 is actuated, which then activates, for example, the control unit 230, which, for example, delays or weights the output of the control signal 240 of the activated control unit 145 in time or in magnitude. In this case, for example, the control unit 145 can be switched on in a delayed manner within a predefined time interval, or the sensor signal 120 used for the control can be provided with a linear, quadratic or exponential weighting within a time interval, and this delayed or weighted sensor signal can be used as an input signal of the control unit 145.

[0035] It is also conceivable that the conversion unit 140 responds to the brake signal 156 of the parking brake or hand brake 157, so that, for example, the regulator unit 145 is converted into a non-activated state because the activated hand brake or parking brake is identified. In this case, it can also be considered that there is no need to adjust the steering.

[0036] In another embodiment, the deactivation of the regulator unit 145 can also be achieved by a conversion unit 140 having a unit that has a similar function to the adjustment unit 230, but Figure 2 Although not shown for reasons of clarity, this unit also carries out a delayed or weighted deactivation (or delayed or weighted deactivation) of the regulator unit 145 .

[0037] Figure 3A diagram 300 is shown of a schematic procedure for weighting or delaying the activation or deactivation of a control unit 145. The time t is plotted on the abscissa of the diagram 300, while the amplification factor F is shown on the ordinate of the diagram 300. The diagram 300 shows a linearly transitioning characteristic curve 310, which represents an amplification or weighting that increases over time, so that within a normalized time interval t, the control unit 145 is loaded with a linearly increasing sensor signal 120. However, the control unit 145 can also be controlled or loaded with the sensor signal 120 by means of an exponential weighting shown by the characteristic curve 320 or a logarithmic weighting shown by the characteristic curve 320. However, any arbitrary association for delay or weighting can also be used, depending on which functional association the user currently desires.

[0038] Figure 4 A flow chart of a method 400 for operating a steering unit for a commercial vehicle is shown. The method 400 comprises a step 410, in which a controller unit of a steering unit of the commercial vehicle is switched to an inactive operating mode or is operated in an inactive operating mode if it is detected that the driver has not given a steering request and if the vehicle speed of the commercial vehicle is less than a predefined threshold value. Furthermore, the method 400 comprises a step 420, in which the controller unit of the steering unit is activated to an active operating mode if it is detected that the driver has given a steering request or if the vehicle speed of the commercial vehicle exceeds a predefined threshold value.

[0039] In summary, it should be noted that with the solution proposed here, a use of a quasi-adaptive regulator with control variable limitation is proposed. The driver torque and the vehicle speed are taken into account as reference points (basis) for this function. For example, if the driver does not request torque and the vehicle speed is low, the steering regulator (or PID regulator) is switched to the standby state. As soon as one of these two conditions is no longer met or both conditions are not met, the regulator, for example, transitions from an inactive state to an active state. The transition from the active state to the inactive state is achieved, for example, by a time-linear function. Depending on customer requirements, the transition function can also be a quadratic function, i.e. a parabolic function, an exponential function.

[0040] What can be called a regulator parameter is that each regulator parameter moves, for example, between two different limits. The upper limit reflects the following situation: in this case, the regulator function is activated. The lower limit reflects the following situation: in this case, the regulator function is deactivated. In the case of a PID regulator, an I component limit can also be set, that is, a limit to the minimum and / or maximum I component can be set. For example, the I component (integrator) can be limited twice and reset when it is not needed. The first limitation of the I component (i.e. not the I parameter) is, for example, carried out indirectly, and is characterized in that the maximum and minimum possible / permissible torque at the steering system is limited (when concerned about function, degradation, etc.). In this way, for example, it is ensured that the regulator cannot provide an excessive (impermissible) torque. This measure is a characteristic of the regulation scheme.

[0041] Other I component limitations can also be performed, wherein the first limitation can be that the two maximum and minimum permissible torques also vary similarly to the PID parameters. The corresponding lower limit is, for example, zero. The second I component limitation can be achieved directly by limiting the I component of the PID regulator with the aid of a time-dependent function.

[0042] It is also possible to set a PID limit, in which case the control variable of the controller is finally limited by the time-dependent function used. It is also possible to use a controller with a precontrol, in which the control concept has a precontrol in addition to the PID controller, which ensures that the control error is reduced rapidly. This means that the reaction time or response of the system to the driver's expectations is hardly affected by this function, because the precontrol component becomes larger as a result. The precontrol can also be configured proportionally to the driver's torque and to the vehicle speed.

[0043] The proposed approach should avoid increased and unnecessary current consumption in the stationary state as much as possible. By limiting the controller, no torque is requested from the motor. In contrast, without a tire relaxation function, the torque is continuously requested by position control (maintaining the position of the previous cycle) rather than by the driver torque (equal to zero).

[0044] In particular, the solution proposed here can influence the oil pressure and the steering angle in the stationary state. When the steering wheel is released, a pressure balance is produced in the two working spaces. In the intermediate position, there are no pulsations of the steering angle and the pressure. The electric motor speed of the electric motor of the hydraulic pump can also be reduced in the stationary state. Not only in the zero position of the steering wheel, but also in any arbitrary position, as long as there is no driver torque and the vehicle speed is low, no active operation of the motor is requested, and thus no torque is requested from the motor.

[0045] With the solution proposed here, a rapid or uncontrolled pressure drop can also be avoided when the steering system is switched off. During an ignition change, for example, the bypass valve also enters a current-free state, thereby short-circuiting the two working spaces. This results in a pressure balance in the two working spaces. In this case, the steering wheel is turned rapidly until the pressure in the respective working space is completely eliminated. As a result, an uncontrolled (unregulated) rapid steering wheel rotation occurs. The rotation speed depends on the pressure and / or any current feedback. As a result, safety issues arise that could result in injuries to the driver or damage to mechanical and electronic components.

[0046] Reference numerals list

[0047] 100 Commercial Vehicles

[0048] 105 Driver

[0049] 110 Steering Wheel

[0050] 115 Sensor

[0051] 120 Sensor signal

[0052] 125 Control unit

[0053] 130 Motion Sensor

[0054] vVehicle speed

[0055] 135 Motion Signal

[0056] 140 conversion unit

[0057] 145 Regulator unit

[0058] 150 Steering unit

[0059] 155 Activation Unit

[0060] 156 Brake signal

[0061] 157 Handbrake

[0062] 160 Hydraulic pump

[0063] 165 Hydraulic circuit

[0064] 170 motion units

[0065] 175 Wheel

[0066] 200 UND connection unit

[0067] 210 Sensor signal comparator

[0068] 220 Motion signal comparator

[0069] 230 Adjustment unit

[0070] 240 Regulator signal

[0071] 300 Graph

[0072] 310 Linear characteristic curve

[0073] 320 Exponential characteristic curve

[0074] 330 Logarithmic characteristic curve

[0075] 400 Method for operating a steering unit for a commercial vehicle

[0076] 410 Conversion Steps

[0077] 420 Activation Steps

Claims

1. A method (400) for operating a steering unit (150) for a commercial vehicle (100), wherein: The method (400) comprises the following steps: - if it is detected that the driver (105) has not given a steering request and if the vehicle speed (v) of the commercial vehicle (100) is less than a predefined threshold value, switching (410) a controller unit (145) of a steering unit (150) of the commercial vehicle (100) into an inactive operating mode or operating the controller unit in an inactive operating mode; and - activating (420) the controller unit (145) of the steering unit (150) into an active operating mode if a steering request predefined by the driver (105) is detected or if the vehicle speed (v) of the commercial vehicle (100) exceeds the predefined threshold value.

2. The method (400) according to claim 1, characterized in that: In the activation step (420), the regulator unit (145) is activated in a delayed manner and / or by means of a weighted, in particular temporally weighted, regulator signal (240).

3. The method (400) according to claim 2, characterized in that: In the activation step (420), the regulator signal (240) is weighted and / or delayed using a linear function, a quadratic function and / or an exponential function.

4. The method (400) according to any one of the preceding claims, characterized in that In the switching step ( 410 ) or the activation step, a value is used as a predefined threshold value for the vehicle speed (v) which represents a maximum walking speed, in particular a value of a maximum of 3 or 5 kilometers per hour.

5. The method (400) according to any one of the preceding claims, characterized in that In the switching step (410) and / or the activation step (420), a PID controller is activated as a controller unit (145).

6. The method (400) according to any one of the preceding claims, characterized in that In the switching step (410) and / or the activation step (420), the regulator unit (145) is controlled in such a way that a physical variable regulated by the regulator unit (145) does not exceed a maximum value and / or falls below a maximum value.

7. The method (400) according to any one of the preceding claims, characterized in that In the switching step (410) and / or the activation step (420), a regulator unit (145) of a hydraulic steering system (150) is actuated, in particular a hydraulic pump (160) of the hydraulic steering system (150) is actuated via the regulator unit (145).

8. The method (400) according to claim 7, characterized in that: In a switching step (410) of a regulator unit (145) of a steering unit (150) of the commercial vehicle (100) from an activated operating mode to an inactivated operating mode, the regulator unit (150) is controlled so that a pressure drop in a hydraulic circuit (165) of the steering unit (150) does not fall below a predefined gradient threshold value, and / or in an activation step (420) of a regulator unit (145) of a steering unit (150) of the commercial vehicle (100) from an inactivated operating mode to an activated operating mode, the regulator unit (145) is controlled so that a pressure increase in the hydraulic circuit (165) of the steering unit (150) does not exceed a predefined gradient threshold value.

9. The method (400) according to any one of the preceding claims, characterized in that In the switching step (410), a controller unit (145) of the steering unit (150) is activated using a brake signal (156) that represents an activated state of a handbrake (157) or a parking brake.

10. A control unit (125) which is designed to carry out and / or control the steps (410, 420) of the method (400) according to any one of the preceding claims in a corresponding unit (140, 155).

11. A commercial vehicle (100) having a control unit (150) according to claim 10. 12 . A computer program, which is designed to carry out and / or control the steps ( 410 , 420 ) of the method ( 400 ) according to claim 1 .

13. A machine-readable storage medium on which the computer program according to claim 12 is stored.

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