RPM-GENERATING SYSTEM WITH IMPROVED POWER RANGE-BASED CONTROL AT ZERO RPM

Abstract

Torque-generating system (10) comprising the following: at least one torque-generating device (12, 16); a transmission (14) with an output element (15); and a control unit (50) for controlling an operation of the system (10) when the output element (15) of the transmission (14) is operating at zero speed, wherein the control unit (50) is programmed to: Determination of a torque requirement level (TR%); Determining an actual rotational speed (ω) A ) of the output element (15); and Determination of an effective rotational speed (ω) E ) of the output element (15) as a calibrated non-zero value using the determined torque requirement level (TR%) when the determined actual rotational speed (ω A ) of the output element (15) is equal to zero; characterized by the fact that the control unit (50) is further programmed to: Calculation of an effective performance (P E ) of the system (10) using the determined effective rotational speed (ω E ) and the determined torque requirement level (TR%); Execution of a control measure with respect to the system (10) using the calculated effective power (P E ), including the transmission of control signals to at least one torque-generating device (12, 16) for selecting a suitable operating mode of the system (10); and to determine the effective rotational speed (ω) E ) by extracting the effective rotational speed (ω E ) from a lookup table corresponding to the determined torque requirement level (TR%), where the respective torque requirement level (TR%) is limited by a maximum and a minimum torque requirement.

Description

TECHNICAL AREA

[0001] This invention relates to a torque-generating system according to the preamble of claim 1 with improved power-range-based control at zero speed. Such a system is essentially derived from DE 10 2013 214 520 A1. BACKGROUND

[0002] Vehicle powertrains and other complex torque-generating systems are typically controlled in response to a requested output torque, depending on the available system output torque. Torque-based control, also known as torque-domain control, provides a single degree of control freedom in the form of available output torque. For example, conventional torque-domain vehicle powertrains are controlled using a driver torque request level, which is determined based on the torque request level and the calibrated set of powertrain-specific gear mapping.

[0003] In contrast, a control unit in a power-range-based control system, or a system controller operating within a power range, considers the total amount of mechanical energy that can be generated by any number of torque-generating devices in the system, such as internal combustion engines and electric motors, as well as any power losses occurring within the system. Power-range control provides two degrees of freedom: both torque and speed. As a result, power-range-based control can be particularly advantageous when used in hybrid-electric powertrains and other complex systems with more than one torque-generating device. SUMMARY

[0004] A vehicle and method are disclosed herein which are intended to improve existing power-range-based control strategies, especially when the torque-generating system operates at or near zero speed. In one embodiment, the torque-generating system can be configured as a hybrid-electric vehicle drive with two or more torque-generating devices, for example, an internal combustion engine and one or more electric machines.

[0005] It is recognized here that, while power-range-based control strategies provide certain performance advantages over torque-range-based control, partly due to their greater degree of freedom, current-based control calculations tend to break down when the controlled system operates at or very near zero output speed. That is, power is the product of output torque and speed, and thus zero output speed corresponds to zero output power. Typical power-range-based control systems therefore ineffectively differentiate between various levels of output torque requests when a system is at or near zero speed. The present disclosure is intended to help address this particular control problem and thereby improve the overall performance of the torque-generating system.

[0006] According to the invention, a torque-generating system is presented which is characterized by the features of claim 1.

[0007] A method for controlling a torque-generating system at zero output speed is also disclosed. The method includes determining a torque demand level and an actual speed of the output element, as well as determining an effective speed of the output element as a calibrated non-zero value. The effective speed is determined as a function of the torque demand level when the actual speed is zero. The method also includes calculating an effective power of the drive train using the determined effective speed and the determined torque demand level. A control action is performed with respect to the torque-generating system using the calculated effective power. The control action may include transmitting drive train control signals to the torque-generating device(s) to select a corresponding operating mode of the system at zero output speed.

[0008] The above-mentioned functions and advantages, as well as other features and benefits of the present disclosure, will become apparent from the following detailed description of the best possible practical implementation of the invention presented, in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of an example vehicle with a control unit programmed to provide power range-based control at or near zero engine speed, as described herein. Fig. 2A-C represent exemplary embodiments of performance curves generated by the control unit of the Fig. 1 can be used with the curves that represent the effective speed, actual speed and torque requirement level. Fig. Figure 3 is a flowchart of an exemplary procedure for providing power range-based control at or near zero speed in a torque-generating system. DETAILED DESCRIPTION

[0009] Referring to the figures, in which similar reference symbols denote similar parts across the multiple views, in Fig. Figure 1 shows an exemplary vehicle 10. A person skilled in the art will recognize that the torque-generating system 10 may be part of a non-automotive vehicle or may be used in non-vehicle applications such as power plants or manufacturing facilities. To maintain consistency in the illustration, the torque-generating system 10 is shown as follows: Fig. 1 is described below in an exemplary automotive context and is therefore referred to as vehicle 10.

[0010] Vehicle 10 from Fig. Section 1 comprises a control unit (C) 50, which is programmed to execute a procedure 100 using computer-readable instructions. The execution of these instructions allows the control unit 50 to provide improved power-range-based control of a powertrain 11 of the vehicle 10 when the vehicle 10 is operating at zero or near-zero output speed. It is recognized here that the mechanical power of a rotating system at zero or near-zero output speed is effectively zero, as mentioned above, regardless of the amount of output torque generated. Therefore, the control unit 50 is programmed to selectively provide a non-zero representation of the effective power of the vehicle 10, or more precisely, of any torque-generating components used in the powertrain 11.This approach is intended to allow the control unit 50 to better distinguish between different torque request levels while the vehicle 10 is running at zero output speed. An intended consequence of the method 100 is to enable the power-based control logic to function in a more optimal manner, without reverting to the use of multiple other control ranges under zero-speed conditions, where control is performed as a function of the magnitude of a requested output torque.

[0011] The control unit 50 of Fig. 1 can be configured as one or more digital computers specifically programmed to execute the instructions of procedure 100, for which an example is given in Fig. Figure 3 shows that the control unit 50 is equipped with sufficient hardware to perform the necessary steps, namely sufficient memory (M), a processor (P), and other hardware such as a high-speed clock, analog-to-digital and / or digital-to-analog circuits, a timer, input / output circuits, and connected devices such as a transceiver, signal programming, and / or signal buffer memory circuits. The memory (M) should include sufficient concrete permanent storage, such as magnetic or optical ROM, flash memory, etc., as well as RAM, EEPROM read-only memory, and the like. In some vehicle configurations, the control unit 50 may be a hybrid control module commonly used in the industry.

[0012] The powertrain 11 can be a hybrid-electric powertrain comprising an internal combustion engine (E) 12, a transmission (T) 14, and an electric machine 16. Additional electric machines 16 are not shown but can be used in other embodiments as known in the art. The motor 12 can be connected to or disconnected from a drive element 13 of the transmission 14 via an input clutch CI, for example, a hydrodynamic torque converter or a friction clutch. An output element 15 of the transmission 14 can be connected to one or more drive axles 18 to provide output torque to a drive gear set 20.

[0013] The electrical power on board the vehicle 10 can be provided via a high-voltage energy storage system 22, e.g., a direct current (DC) battery pack and associated power electronics. The energy storage system 22 can be connected to an inverter module 24, which, as is known in the art, includes semiconductor switches and other electronic components that respond to pulse-width modulation or other switching signals to convert a DC output voltage from the energy storage system 22 into a suitable multiphase voltage for powering the electric machine 16 and vice versa.

[0014] Thus, as part of the powertrain architecture 11, a DC bus 21 can electrically connect the on-board energy storage system 22 to the inverter module 24, and an AC bus 23 can electrically connect the inverter module 24 to the electric machine 16. Further components can be used as part of the on-board network to supply the various components of the powertrain 11, including, for example, an auxiliary module, an auxiliary battery, and one or more auxiliary voltage devices, which are located in Fig. 1 omitted for exemplary simplification.

[0015] The in Fig. The powertrain 11 shown in Figure 1 is an example of a system that experiences power losses as a byproduct of energy conversion and storage. For example, the fossil fuel burned by the engine 12 can generate a known amount of available mechanical power. Similarly, electrical energy from the high-voltage on-board energy storage system 22 can be used to generate a known amount of electrical energy. However, the total available power for driving the drive wheels 20 is reduced by power losses occurring in the powertrain 11, based on the sum of the available fuel and battery power. For example, the fuel combustion process generates some losses, and electrical power losses occur due to electrical loads on the respective DC and AC buses 21 and 23, as well as during the operation of low-voltage components.Further mechanical power losses occur in the gearbox 14 and in the electric machine(s) 16. The inertia of the motor 12, braking system losses, and other potential losses reduce the amount of available power that can be supplied to the drive axles 18. It is therefore necessary for power-range-based control logic to correctly account for such losses in order to ultimately determine the output power available at the drive wheels 20.

[0016] Mathematically, the output power of a torque-generating device is the product of the torque and the output speed of the device. In the power domain, the total power consumption of the vehicle 10 and the output power requested by a driver are used as inputs for several powertrain selection functions. As is known in the engineering field, powertrain state selection functions are used in the control logic to determine the most suitable operating state for arranging given actual operating conditions. In other words, the power balance of the powertrain 11 is optimized by determining which components should be switched on or off at a given time and subsequently controlling the appropriate operating states.

[0017] The control unit 50 of Fig. Control unit 50 thus determines when to switch motor 12 on or off, which gear of transmission 14 to select, and whether and / or how much to charge or discharge the high-voltage energy storage system 22. Control unit 50 also determines a suitable input speed for transmission 14 and a suitable level of motor torque, which must be applied by motor 12 upon command. Powertrain control signals (arrow CC) are then transmitted by control unit 50 to the various components of the powertrain 11, including motor 12, transmission 14, inverter module 24, and electric machine 16, to arrange a specific combination of fuel and electricity that ultimately minimizes power loss in the powertrain 11.All conventional selection functions can benefit from the use of effective power at zero speed, as described below, since effective power differentiates between high-torque and low-torque stages at or near zero vehicle speed 10.

[0018] As part of the present control architecture, the control unit 50 is the Fig. 1 programmed with an effective speed logic block 25. The effective speed logic block 25 can be implemented in various ways, for example as one or more lookup tables defined by a torque requirement level (TR%) and an actual speed (ω). A ) of the output element 15 are indexed and referenced. The torque requirement level (TR%) and the actual rotational speed (ω) A ) can be from a respective position sensor (S P ) of an accelerator pedal 17 and a transmission output speed sensor (S O), which is arranged opposite the output element 15, can be measured or determined using other measured, calculated or estimated rotational speed values.

[0019] The torque request level (TR%) is a percentage or amount of output torque requested by the driver or another operator of the system 10. For example, when using an accelerator pedal 17 and a brake pedal to determine a driver request, full application of the accelerator pedal with zero application of the brake pedal (not shown) can be considered a request for a 100% torque request level, or a request for all available torque from any available drive unit of the system 10. The torque request level (TR%) is treated here as a suitable representation of driver-requested output torque or axle torque; that is, the level of output torque that a driver of the vehicle 10 expects in response to increased pressure on the accelerator pedal 17 or increased force on another torque request level input device.In other words, the control unit 50 is programmed to determine, for each given speed requirement level (TR%), the output torque in Newton meters (Nm) requested by the driver, e.g. via a lookup table or calculation.

[0020] The control unit 50 multiplies the output torque requested by the driver by an effective rotational speed, which is used by the effective power logic block 25 to determine an effective power value P. E was determined, i.e. T R · ω E = P E , where T R the output torque requested by the driver and (ω E) the effective speed. As part of the procedure 100, the effective power logic block 25 therefore represents any software and associated hardware elements of the control unit 50 that together provide a calibrated effective speed at an actual output speed at or near zero in order to temporarily supply a calibrated torque-requirement-indexed non-zero speed value to any power-based selection decision process of the control unit 50.

[0021] Fig. 2A-C illustrate, for example, three possible profiles or data curves for determining the effective rotational speed (ω). E ) at zero speed conditions, with respective curves 60, 62 and 64, which show a calibrated correlation between actual speed (ω A ) as plotted on the horizontal axis and effective rotational speed (ω) E) as plotted on the vertical axis, for example in the specified data curve form or in a corresponding reference table. Fig. 2A represents the effective rotational speed (ω) E ) under positive torque request conditions, i.e. when a driver of vehicle 10 or an operator of another torque-generating system requests output torque in a positive or forward direction of rotation. Fig. 2B represents the effective rotational speed (ω) E ) under zero-torque conditions, when the driver / operator does not actively request an output torque, for example, when there is no pressure on the accelerator pedal 17 of the Fig. 1 is exercised. Fig. 2C represents the effective rotational speed (ω) E ) under negative torque requirement conditions, for example, when the driver / operator requests output torque in a negative or reverse direction of rotation.

[0022] With reference to Fig. 2A and Fig. 2C corresponds to point 35 of a maximum torque requirement level, for example 100% application of the accelerator pedal 17 of the Fig. 1. Such a scenario can easily occur as soon as the vehicle 10 is idling at a red light, followed by the driver fully depressing the accelerator pedal 17 when the light turns green. As in Fig. 2A can determine the actual rotational speed (ω) A ), as soon as the actual rotational speed (ω A ) sufficiently zero, as shown in point 38, can be used by the control unit 50 to control the drive train 11. Thus, at low or zero actual speed, the control unit 50 can use an effective speed (ω) calibrated by the above-mentioned effective speed logic block 25. E ) replace. A separate lookup table or curve can be used, similar to those of the Fig. 2A and Fig. 2C, or different depending on the design, are used for lower torque requirement levels at or near zero speed to provide a desired control response. Separate lookup tables of performance curves for 10–20% torque requirement, 21–30% torque requirement, 31–40% torque requirement, etc., can be programmed in memory M, for example.

[0023] Fig. Figure 2B shows zero-torque demand conditions. Under such conditions, the effective speed (ω) E ) a linear function of the torque requirement and the actual speed (ω A ) over the entire operating range. Such a procedure treats the actual speed as measured by the output speed sensor S. O the Fig. 1 measured as the effective rotational speed and vice versa.

[0024] Referring to Fig. 3 begins an exemplary embodiment of the method 100 with step S102, wherein the control unit 50 is made of Fig. 1 the measured actual rotational speed (ω A ) and the measured torque requirement level (TR%) from the respective sensors S O and Sp receives or otherwise determines these values. Procedure 100 then proceeds to step S104.

[0025] In step S104, the control unit 50 processes the actual rotational speed (ω). A ) and the measured torque requirement level (TR%) from step S102 via the effective speed logic block 25 to determine the effective speed (ω E Step S104 can extract the effective rotational speed (ω). E ) from a lookup table according to the measured torque requirement level, where the effective speed (ω) E) a sufficiently high non-zero value, such as 5-7 km / h or approximately 5-10 km / h. For example, several data tables of sufficiently high resolution can be programmed into memory M of the control unit 50 to cover a full range of possible torque request levels, including fully or widely opened torque requests as in Fig. 2A and Fig. 2C shown and zero torque requirement as in Fig. Figure 2B shows that procedure 100 proceeds to step S106 once the effective rotational speed has been determined.

[0026] Step S106 includes calculating the effective power (P EFor example, the control unit 50 can determine the output torque requested by the driver as a function of the torque request level (TR%), for example using a torque-to-position table, which is known in the art. Once the output torque requested by the driver is known, this value can be derived from the effective speed in step S104 to determine the effective power.

[0027] In step S108, the control unit 50 determines whether the actual rotational speed (ω) A ) of the vehicle 10 is approximately zero, for example, less than approximately 5 km / h in an exemplary embodiment. If so, the method 100 continues with step S110. Otherwise, the method 100 continues with step S112.

[0028] In step S110, the control unit uses 50, after determining in step S108 that the actual rotational speed (ω) A) is approximately zero, the derived effective power (P E ) from step S106 to execute a control action (CA1) with respect to system 10. Step S110 can transmit the powertrain control signals (arrow CC of the Fig. 1) include one or more torque-generating components of the drive train 11, for example the electric machine 16 and / or the motor 12 and / or the various electrical components relating to Fig. 1. In this way, the control measure can include selecting a suitable drive train operating mode.

[0029] Step 112 involves executing another control action (CA2) including using the actual rotational speed (ω). A ) to calculate the effective power (P ESteps S110 and S112 are effectively the same in some embodiments, as step S106 involves calculating the effective power using data tables or curves that could easily be extended to include zero actual rotational speeds, as in the Fig. 2A-2C is shown. In other words, as soon as the actual rotational speed increases above a limiting speed, for example above point 38 of the Fig. 2A and Fig. 2C, actual and effective rotational speeds are the same, and therefore there is no difference between actual and effective power.

[0030] By implementing Method 100, the complexity of hybrid powertrains or other complex torque-generating control systems can be reduced, thereby facilitating calibration through the extensive use of a single control range, i.e., the power range. Method 100 can therefore improve the overall system response at or near zero speed by overcoming the existing inability to differentiate across torque levels at zero speed. The system's total power consumption, even at or near zero speed, can be used as an input to several selection functions for arranging the most efficient operating state under given running conditions.

Claims

[1] Torque-generating system (10) comprising the following: at least one torque-generating device (12, 16); a transmission (14) with an output element (15); and a control unit (50) for controlling an operation of the system (10) when the output element (15) of the transmission (14) is operating at zero speed, wherein the control unit (50) is programmed to: Determination of a torque requirement level (TR%); Determining an actual rotational speed (ω) A ) of the output element (15); and Determination of an effective rotational speed (ω) E ) of the output element (15) as a calibrated non-zero value using the determined torque requirement level (TR%) when the determined actual rotational speed (ω A ) of the output element (15) is equal to zero; characterized by , that the control unit (50) is further programmed to: Calculation of an effective performance (P E ) of the system (10) using the determined effective rotational speed (ω E ) and the determined torque requirement level (TR%); Execution of a control measure with respect to the system (10) using the calculated effective power (P E ), including the transmission of control signals to at least one torque-generating device (12, 16) for selecting a suitable operating mode of the system (10); and to determine the effective rotational speed (ω) E ) by extracting the effective rotational speed (ω E ) from a lookup table corresponding to the determined torque requirement level (TR%), where the respective torque requirement level (TR%) is limited by a maximum and a minimum torque requirement. [2] Torque-generating system (10) according to claim 1, wherein the at least one torque-generating device (12, 16) comprises an internal combustion engine (12) or an electric machine (16). [3] Torque generating system (10) according to claim 1, further comprising a drive axle (18) with a set of road wheels (20), wherein the torque generating system (10) is a vehicle powertrain (11). [4] Torque-generating system (10) according to claim 1, further comprising a speed sensor (S O ), operable for measuring the actual rotational speed (ω) A ) and a position sensor (S P ), operable for measuring the torque requirement level (TR%), wherein the control unit (50) is used to determine the actual speed and the torque requirement level (TR%) by obtaining the actual speed (ω) A ) and the torque request level (TR%) from the speed sensor (S O ) and from the position sensor (S P) is programmed in each case. [5] Torque-generating system (10) according to claim 1, wherein the control unit (50) is programmed to control the effective power (P E ) by determining a driver-requested output torque of the transmission (14) as a function of the torque request level (TR%) and then calculating the effective speed (ω E ) multiplied by the output torque requested by the driver.

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