DE102007049253B4 - Method for controlling a power split transmission - Google Patents

Abstract

Method for controlling a power-splitting transmission which has an internal combustion engine and at least two electric machines (E1, E2) mechanically coupled via gear stages, which are arranged in the power flow of the transmission in such a way that the transmission ratio of the transmission through that of the respective electric machine (E1, E2) applied torque and / or the rotational speed is determined and the electric machines (E1, E2) are coupled via the transmission elements, wherein the control of torque and / or rotational speed of the electric machines (E1, E2) is carried out with the following method steps:
on the basis of at least one current operating parameter of the electric machines, one is selected as the leading electric machine (E1 / E2) for controlling the electric machines (E1, E2), the leading electric machine being selected on the basis of their speed signal (Dz_E1 / 2_act), respectively the higher speed electric machine (E1 / 2) is selected as the leading one
- Based on the driver's request based on consumption and / or performance criteria, a determination of the optimal speed of the internal combustion engine (Dz_Vm_opt)
based on the driver's request and the speed of the internal combustion engine (Dz_Vm_ist), a torque (Dm_E1 / 2_soll) and / or a speed setpoint for the set as leading electric machine is formed, wherein the target value determination for the following electric machine by means of a performance consideration taking into account by the Electric machines available speed or torque occurs.

Description

Previously known are transmissions which continuously regulate the ratio between the input and output of a transmission by means of a combination of mechanical transmission elements and an at least partially electrical transmission of the power flow.

An example of such a transmission is in the Scriptures DE 103 14 234 B3 described. This is a 4-shaft power split transmission, which has an internal combustion engine on the drive side and whose output is coupled via a planetary gear to the drive side. The internal combustion engine thereby drives a planet carrier, on which a three-stage stepped planetary gear is rotatably arranged. A first stage drives the sun gear of the transmission output, a second stage of the planet carrier engages directly in a sun gear, which is coupled to a first electric machine and a third stage of the stepped planet engages via intermediate gears in the sun gear, which is connected to a second electric machine. By controlling the electric machines, the transmission ratio of the transmission is set. By determining the speed of an electric machine and the fixed speed of the output results in a ratio between internal combustion engine and output. This transmission ratio can be infinitely adjusted via the choice of the electric machine speed. If none of the electric machines is driven or braked, then no support torque is generated by the electric machines. The only moment of resistance on the stepped planet thus comes from the output, which corresponds to a function idling without power transmission from the internal combustion engine. At standstill each one of the electric machines is in each case a stand translation. There is no power transmission by electrical means. In all other operating points of the transmission one of the electric machines works as a generator and one as a motor. By electrical means so a power flow. The transmission is also suitable for a hybrid vehicle when an energy storage is arranged in the electric power flow. Without energy storage, the transmission is operated electrically balanced, the output power of an electric machine is equal to the recorded power of the other electric machine.

The transmission is infinitely electrically adjustable in terms of its translation and can work by energy storage in the electrical branch with energy production and the delivery of electrical energy from the memory, so that the transmission for use in a hybrid vehicle, the functions of recuperation and boost during acceleration can fulfill. A purely electric driving is also possible when feeding the electric machines from the energy storage.

The control for such a transmission is complex because of the complexities. Possible is the separate control of the internal combustion engine and the translation controlling electric machines. A separate control of the two electric machines and the internal combustion engine, which is controlled by the setpoint specifications of a control unit is in the DE 103 33 931 A1 described. In the illustrated power split transmission with a downstream manual transmission, a desired value specification with respect to torque and rotational speed of the internal combustion engine for both electric machines takes place from a control device. With separate control loops, the setpoint for the respective drive is converted. The electric machines are separately controlled by a single controller, wherein a speed control with formation of a control difference to the setpoint takes place by recording the actual speed value of the electric machine for each of the electric machines individually. The control of the electric machines is based on separate control circuits, the control is coordinated by the setpoint input in the control unit. The high number of existing degrees of freedom of the transmission requires a very complex control.

According to the DE 10 2005 061 414 A1 is a method of operating a power-split hybrid drive having at least first and second electric machines coupled via a transmission and an engine outputting torque, the prior art, wherein the electric machines and the internal combustion engine are drivingly connected, at least temporarily controlling the first electric machine and the second electric machine are torque-controlled, wherein the internal combustion engine is operated speed-controlled.

According to the DE 103 93 594 T5 is a prior art drive unit combined with fuel and electric power, combined with a combustion engine, an engine, a clutch, a transmission, a traction battery, a brake system, and an overall vehicle controller, combined in a drive system for a two-engine hybrid vehicle a main motor, an auxiliary motor, a mechanical step transmission, a rotor shaft of the main motor connected to the output shaft of the transmission, a rotor shaft of the auxiliary motor connected to a crankshaft of the internal combustion engine by means of a drive mechanism, and the main motor and the auxiliary motor are electrically connected to a drive battery. By controlling the Overall vehicle control, the vehicle can be automatically driven by the hybrid drive system in the following working modes: pure motor drive mode, row drive mode, parallel drive mode, hybrid drive mode, standby stop mode of the engine, brake energy recovery mode, independent drive mode of the internal combustion engine and auxiliary drive mode during the shift.

The object of the invention is therefore to provide a simple control algorithm that allows for a power-splitter transmission flexible control of the translation via the control of at least two electric machines.

Advantageously, according to the invention, a performance-based approach is used, wherein the calculation of the manipulated variables for the electric machines takes place in such a way that, starting from an electric machine specified as leading, a calculation of the rotational speed and / or the torque of both electric machines takes place together. In a simple way, electrical and mechanical manipulated variable restrictions are taken into account for the calculation of the setpoint values.

The method for controlling a power-split transmission is based on a configuration in which an internal combustion engine and at least two electrically connected via gear stages electric machines are present, the electric machines are arranged in the power flow of the transmission such that the transmission ratio of the transmission by that of the respective electric machine applied torque and / or the rotational speed is determined and the electric machines are coupled to each other via the transmission elements. By determining the speed of an electric machine and the speed of the output, the transmission ratio of the transmission is determined. It may be advantageous to a 4-shaft power split transmission with a technical design analogous to that in the DE 103 14 234 B3 act described transmission. The disclosure of the DE 103 14 234 B3 is explicitly included here. However, the control method is also applicable to other power split transmission with electrical and mechanical transmission path of said configuration.

The control of the described transmission takes place in such a way that, on the basis of a current operating parameter of the electric machines, for example the rotational speed for the control of the electric machines, one of the electric machines is selected as the electric machine leading to the calculation of the desired values. The speed signals of the electric machines provide easily measurable information about the operating state of the machines. Electric machines have a large change in efficiency in low-speed areas, making control systems with electric machines highly sensitive at low speeds. When operating the system according to the invention, the machines can change their direction of rotation. If such a zero crossing takes place in an electric machine, the other electric machine inherently has a higher speed. It proves to be convenient to use the machine at higher speeds than leaders in such operating points, since the system reacts to manipulated variable changes thus less sensitive. The speed signal is therefore particularly suitable for the selection of the leading electric machine. Determining for the transmission control is the driver's request. Based on the torque desired by the driver, which is detected for example with the position of the pedal, takes place based on consumption and / or performance criteria, a determination of the speed of the engine. Here, for example, from the consumption map for the engine a best point can be selected and the engine is then driven with a consumption-optimal speed. With the predetermined speed of the internal combustion engine, a torque and / or speed setpoint for the set as leading electric machine is formed, wherein the target value determination for the following electric machine by means of a performance consideration taking into account the deliverable by the electric machines in the current speed operating point torque.

For electrically balanced operation, starting from the leading electric machine, the power output or absorbed by the leading electric machine is set equal to the power consumed by the following one. The performance values are the same in terms of their amount, but were calculated with different signs.

Advantageously, according to the invention, the operating modes boost, assist, recuperation and charging are realized via the detuning of the power balance of the two electric machines. In Boost operating mode (support of the combustion engine at full load) and assistants (support of the combustion engine in operating ranges outside full load), energy is drawn from the energy store, while during recuperation (regeneration of braking energy) and energy storage, an energy flow to the energy store takes place. In a simple way, a setpoint control for these operating ranges can be realized with the detuning of the power balance. If the energy storage to be charged, the power balance of the electric machines is detuned to the effect that a positive power surplus is generated. The generator-operated electric machine generates more power than is consumed by the motor-driven. This results in a generator torque, which would lead to a change in the transmission ratio. The speed controller for the internal combustion engine tries to reduce this control difference and increases depending on the application, the throttle angle or the injection quantity. This is equal to a load point increase of the internal combustion engine. The energy surplus is then supplied to the energy store. In the reverse case, that an additional drive torque is to be generated, the power consumption of the following electric machine is set greater than the power that generates the leading electric machine. The additional energy is taken from the energy storage.

In a simple form of the selection algorithm of the leading electric machine, this is determined on the basis of the speed signal, with the electric machine always being selected at a higher speed than the leading one. It is thus avoided that an electric machine forms the basis for the calculation of the setpoint values when the rotational speed is reversed at the zero crossing of the rotational speed. In a further development of the method, a switch between leading and following electric machine can take place when the leading electric machine reaches a lower speed threshold and the speed of the following electric machine is above this threshold. The switchover therefore only takes place when the leading electric machine approaches the speed zero point.

The method according to the invention advantageously includes consideration of the electrical and mechanical limits of the electric machines. Based on the actual speed value and the torque setpoint of the leading electric machine, the mechanical power to be delivered or absorbed is calculated and converted into a power output to be delivered or absorbed by the efficiency of the electric machine. Based on a threshold value of the maximum electric power at the currently applied speed, the electric power is limited to the maximum value when the threshold value is exceeded. Subsequently, for the operating mode in electrically balanced operation without energy storage, the electrical power of the following electric machine to be dispensed or set is set equal to the electric power of the leading electric machine to be dispensed or received, which is equal in magnitude, but whose sign is different and from the desired value thus determined the electric power and the speed actual value of the following electric machine, the torque to be delivered is calculated, based on the electric machine-specific maximum torque determined taking into account the actual speed of the electric machine, a check whether the following electric machine can convert the required torque and torque when exceeding the limit is limited to the maximum torque. Starting from the max. Torque takes place with the speed actual value of the following electric machine, a conversion into the required electrical power of the following electric machine. The reference variable of the electric power calculated in this way is also specified with the opposite sign (identical in terms of amount) as the desired value of the electrical power of the leading electric machine. According to the invention, the advantage is achieved that the manipulated variable limitations of the electric machines are taken into account in the setpoint specification. By the computing path on both electric machines, which considered as the starting point of the leading electric machine and with the manipulated variable limiting this and the following back to the leader, it is ensured that both electric machines can implement the required to be given or absorbed power. At the same time an electrically balanced operation is realized.

In an advantageous development, starting from the electric powers of the electric machines with the respective actual value of the speed, the torque of the respective electric machine to be dispensed or to be picked up is calculated and set with a suitable subordinate control.

The inventive method will be described below with reference to an embodiment.

This shows 1 an overview of the basic structure of the tax procedure and 2 a detailed representation of the setpoint specification for the electric machines.

1 shows the basic structure of the regulatory procedure. Based on the driver's request, via the signal of a pedal encoder PWG is measured and the current vehicle speed v_Fzg will be in a performance interpreter 1 a desired wheel torque Dm_Rad_soll determined. At the same time via a consumption map, the specification of the determined from the point of view of fuel consumption as optimal speed Dz_Vm_opt for the internal combustion engine. A control device, here for example a throttle valve controller 2 , is based on the respective optimum speed Dz_Vm_opt and the measurement of the actual speed of the internal combustion engine Dz_Vm_ist for adjusting the desired consumption-optimal engine speed Dz_Vm_opt used, for this purpose the position of a throttle valve Pos_Throttle is regulated. Alternatively, the injection quantity could be calculated here, for example, for a diesel engine and adjusted accordingly.

Parallel to the setpoint specification for the internal combustion engine, based on the transmission-specific constraints, the desired wheel torque Dm_Rad_Soll and the speeds of all transmission shafts are used in a feedforward control 4 the pre-tax setpoints for the electrical machines E1 . E2 calculated. These are the torque Dm_E1_v and Dm_E2_v of the electric machines to be realized by the precontrol E1 . E2 , Input variables of the feedforward control are the desired wheel torque Dm_Rad_soll , the actual speed value of the wheel Dz_Rad_ist and the internal combustion engine Dz_Vm_ist and the electric machines Dz_E1_ist . Dz_E2_ist , Parallel to the pilot control are in a speed controller 3 from the actual speed of the internal combustion engine Dz_Vm_ist and the optimal engine speed Dz_Vm_opt the set torques of the electric machines Dm_E1_Dr and Dm_E2_Dr determined. The pre-control realizes the implementation of the desired wheel torque while the speed controller compensates for the difference between the motor setpoint and the actual motor speed. The from the speed controller 3 and the pilot control 4 determined moments are summed up. The torque setpoints of the electric machines Dm_E1_soll . Dm_E2_soll result from the summation of the torque value from pilot control and speed controller. ( Dm_E1_soll = Dm_E1_Dr + Dm_E1_v ; Dm_E2_soll = Dm_E2_Dr + Dm_E2_v ) The nominal value of the torque for the respective electric machine Dm_E1_soll and Dm_E2_soll and the actual speed values of the electric machines Dz_E1_ist and Dz_E2_ist are the input variables of the electric machine control 5 , at whose output the requested electrical power P_E1_gef and P_E2_gef is passed to the electric machine control a subordinate control to form the control variables. This can be, for example, the frequency of an inverter for controlling the electric machines E1 . E2 his.

The electric machine control 5 is detailed in 2 described. Input variables of the electric machine control 5 are - how to 1 described - the target torque Dm_E1_soll and Dm_E2_soll and the actual speed values of the electric machines Dz_E1_ist and Dz_E2_ist , The electric machine control 5 generates the required electrical power at its output P_E1_gef and P_E2_gef or from these the required torques of the electric machines Dm_E1_gef and Dm_E2_gef , With the help of the electric machine control 5 Both balanced electrical operation and operation in the recuperation, charging, assisting and boosting operating areas are realized. Starting point of the control is a performance consideration for the electric machines in the context of the power split transmission. With the help of the actual speed signal of the electric machines Dz_E1_ist and Dz_E2_ist becomes an electric machine E1 O. E2 selected as the leading electric machine. In a simple implementation, the leading electric machine is the one with the respective higher speed. The calculation of the setpoint values starts from the desired torque of the leading electric machine. If the leading electric machine E1 is, the calculation goes from Dm_E1_soll and the speed Dz_E1_ist the leading electric machine E1 out. With knowledge of the efficiency phi will be the desired electrical power P_E1_w calculated. Based on the speed Dz_E1_ist and a specific electrical machine known limit for the electric machine at this speed is the desired performance P_E1_w limited. Starting from the electrically balanced operation, the electric power of the following electric machine must be the same in terms of magnitude, but with different signs. (P_E2_w = (-1) × ( P_E1_w )). Thus, the desired performance of the following electric machine is determined from the limited in terms of its possible manipulated variable value of the leading electric machine. From the thus determined desired power of the following electric machine ((-1) × ( P_E1_w )) is at their actual speed Dz_E2_ist the internal torque Dm_E2_int the following electric machine calculated. The torque is at the current speed Dz_E2_ist the following electric machine E2 Based on an electromachine-specific limit value when it is limited to the predetermined maximum value. It is thus the performance of the second electric machine E2 at their actual speed introduced into the calculation of the setpoints. With the actual speed of the electric machine Dz_E2_ist and the efficiency phi the calculation of the required electrical power consumption takes place P_E2_gef , which with opposite sign than the required electric power P_E1_gef the leading electric machine is specified as a setpoint. The absorbed or delivered power P_E2_gef and P_E1_gef The electric machines is by taking into account the limits of the respective electric machines E1 . E2 at their respective current speed can be implemented by the electric machines. The limits of both electric machines are considered when specifying the setpoints. Alternatively, for a torque-based control of the electric machines from the required electrical power P_E1_gef and P_E2_gef with the respective actual speeds of the electric machines their required torque Dm_E1_gef and Dm_E2_gef determined and passed to a lower-level torque controller for controlling the electric machines.

In the event that the electric machine E2 as the leader is selected, the calculation of the setpoints is done analogously. The calculation branches by means of the position of the switches S1 - S4 which are reversed so that the calculation is carried out analogously to the method described above for the then leading electric machine.

In an extension for operation with an energy storage is the ratio of the required electrical power P_E1_gef and P_E2_gef , which are equal in terms of amount in the electrically balanced operation, deliberately detuned. A discharge of electrical energy to the memory or a supply of energy from the memory is characterized by the then different setpoint default of P_E1_gef and P_E2_gef realized. An energy management 6 calculates at least from the input variables Dz_E1 / 2_ist and the battery voltage u_Batt the desired additional electrical power, as a contribution to performance P_Add_1 / 2 the performance required for the balanced operation P_E1 / 2_gef is superimposed. The amount of the required additional service is calculated by a higher-level energy management system.

LIST OF REFERENCE NUMBERS

1

power interpreter

2

throttle controller

3

Speed governor

4

feedforward

5

Electric machine control

6

energy management

S_1 ... 4

Branching of the calculation

PWG

Signal pedal encoder

v_Fzg

vehicle speed

Dm_Rad_soll

desired wheel torque

Dm_Rad_ist

Actual value of the wheel torque

Dz_Vm_opt

Optimum engine speed

Dz_Vm_ist

Actual speed internal combustion engine

E1, E2

electric machines

Dz_E1 / 2_ist

Actual value of the speed of the electric machine E1 or. E2

Dz_E1 / 2_soll

Setpoint of the speed of the electric machine E1 or. E2

Dm_E1 / 2_v

Torque setpoint of the electric machines from the pilot control

Dm_E1 / 2_soll

Setpoint of the torque of the electric machine E1 or. E2 at the entrance of the electric machine control 5

P_E1 / 2_w

desired electrical power consumption / output limited based on the actual speed and the power-specific capacity

Dm_E1 / 2_int

calculated internal torque limited based on the actual speed and the electromechanical performance

P_E1 / 2_gef

required delivered / recorded el. Power of the electric machine at the output of the electric machine control

Dm_E1 / 2_gef

Required torque of the electric machines at the output of the electric machine control

u_Batt

battery voltage

P_Add_1 / 2

power contribution

Pos_Throttle

throttle position

Dz_Rad_ist

Actual speed of the wheel

phi

efficiency

Claims (7)

Method for controlling a power-splitting transmission which has an internal combustion engine and at least two electric machines (E1, E2) mechanically coupled via gear stages, which are arranged in the power flow of the transmission in such a way that the transmission ratio of the transmission through that of the respective electric machine (E1, E2) applied torque and / or the speed is determined and the electric machines (E1, E2) are coupled via the gear elements, wherein the control of torque and / or rotational speed of the electric machines (E1, E2) takes place with the following method steps: - on the basis of at least one current operating parameter of the electric machines is for the control of the electric machines (E1, E2) is selected as a leading electric machine (E1 / E2), the leading electric machine being selected based on its speed signal (Dz_E1 / 2_act), with the higher speed electric machine (E1 / 2) selected as the leading one - Based on the driver's request based on consumption and / or performance criteria, a determination of the optimal speed of the engine (Dz_Vm_opt) - based on the driver's request and the engine speed (Dz_Vm_ist) is a torque (Dm_E1 / 2_soll) and / or Speed setpoint for the established as a leading electric machine formed, the setpoint mitit tion for the following electric machine by means of a performance consideration taking into account the available through the electric motor speed or torque. Method according to Claim 1 , characterized in that for the electrically balanced operation in which no energy storage is charged or discharged, the output from the leading electric machine power is equal to that taken by the following or recorded in the case of power consumption of the leading electric machine from the leading electric machine Power is equal to that of the following delivered power. Method according to Claim 1 , characterized in that for the operation of the electric machines with an intermediate energy storage that recorded by this or requested by this power for the balanced electric power balance is considered and thus the operating modes boost and recuperation are realized on the detuning of the power balance of the two electric machines. Method according to Claim 1 . 2 or 3 , characterized in that a switchover between leading and following electric machine takes place when the leading electric machine reaches a lower speed threshold and the speed of the following electric machine is above this threshold. Method according to one of the preceding claims, characterized by the following method steps: - an optimum speed (Dz_Vm_opt) for the internal combustion engine and a desired wheel torque (Dm_Rad_set) is determined from the driver request determined via a pedal value generator (PWG) and the vehicle speed (v_Fzg) - with the speed of the internal combustion engine (Dz_Vm_ist) and the optimum speed (Dz_Vm_opt) as a setpoint, a speed control device for the internal combustion engine is applied - the torque setpoint (Dm_E1 / 2_soll) is a portion of the pilot control, which is the actual speeds of the internal combustion engine (Dz_Vm_ist) and the electric machines (Dz_E1 / 2_ist ) and the applied wheel torque (Dm_Rad_ist) and from a proportion of a speed controller (3), which evaluates from the respective optimum speed of the internal combustion engine (Dz_Vm_opt) and their actual speed (Dz_Vm_ist) formed - an electric machine control (5) determines from the Dr ehmomentsollwerte (Dm_E1 / 2_soll) and the speed actual values of the electric machines (Dz_E1 / 2_ist) the required output or input power (P_E1 / 2_gef). Method according to one of the preceding claims, characterized by the following method steps: - selection of one of the electric machines (E1, E2) on the basis of the speed comparison of the actual speeds (Dz_E1_ist, Dz_E2_ist) - starting from the torque setpoint (Dm_E1 / 2_soll) of the leading electric machine and its speed list signal ( Dz_E1 / 2_ist) whose mechanical power to be delivered or absorbed is calculated and converted with the efficiency of the electric machine into a desired electrical output (P_E1 / E2_w) to be delivered or picked up, based on an electromachine-specific limit value of the capacity of the electric machine at the instantaneous actual speed (Dz_E1 / 2_ist) there is a performance limitation of the achievable by the electric motor power, wherein the electric power is limited when the limit value is exceeded - below is the electrically absorbed operation without energy storage the male or to be submitted ele ktrische performance of the following electric machine equal to the output or aufzunehmenden electric power of the leading electric machine but set with different signs - from the desired electrical power of the following electric machine, an internal torque is calculated (Dm_E1 / 2_int) calculated with an electromachine specific limit of the performance of Electric machine at the current actual speed (Dz_E1 / 2_ist) is limited to the maximum deliverable or absorbable torque when exceeding the limit - the thus limited internal torque (Dm_E1 / 2_int) is in the following with the speed actual value of the following electric machine (Dz_E1 / 2_ist) in the Required electrical power of the following electric machine converted and given the opposite sign in terms of absolute value as desired value of the required electrical power (P_E1 / 2_gef). Method according to Claim 5 or 6 , characterized in that from the target value for the respectively required electric power (P_E1 / 2_gef) of the electric machines (E1, E2) and the actual speed of the respective electric machine (E1, E2) the torque to be delivered or absorbed (Dm_E1 / 2_gef) of the respective Electric machine is calculated.

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