Method for controlling, more particularly in a closed-loop manner, a powertrain test bench with real transmission

Abstract

The invention relates to a method for controlling, more particularly in a closed-loop manner, a test bench for a powertrain with a real transmission, the method including calculating a desired value of a control parameter, more particularly a desired rotational speed, at the transmission output of the real transmission by means of a model that represents the transmission and at least one further component, more particularly a shaft, of the output side of the powertrain as virtual components, on the basis of at least one measurement parameter, more particularly a rotational speed and/or a torque, measured on the powertrain; and controlling the test bench, more particularly a load machine, on the basis of the desired value.

Claims

1. A method for controlling a test bench for a powertrain having a transmission, comprising the following method steps: operating the transmission on the test bench as a real component; calculating a desired value of a control parameter of a transmission output of the transmission on a basis of a model that simulates the transmission and at least one component of an output side of the powertrain other than the transmission as virtual components, wherein the at least one component of the output side of the powertrain is not assembled on the test bench in reality but only exists as one of the virtual components and the transmission is both assembled on the test bench in reality and simulated as one of the virtual components, on a basis of at least one measurement parameter measured on the powertrain; and controlling the test bench on a basis of the desired value of the control parameter.

2. The method according to claim 1, wherein the model factors in properties of a vehicle and properties of a track surface.

3. The method according to claim 1, wherein the model factors in at least one input torque of the transmission.

4. The method according to claim 1, further comprising the following method step: calculating an input torque of the transmission on a basis of an axial moment of inertia of the transmission, an angular acceleration of the transmission output of the transmission, and a measured torque of the transmission output of the transmission.

5. The method according to claim 4, wherein a dynamic torque calculated from the angular acceleration of the transmission output of the transmission and the axial moment of inertia of the transmission is added to the measured torque of the transmission output of the transmission.

6. The method according to claim 4, wherein a respective gear ratio of the transmission to be tested is taken into account when calculating the input torque of the transmission and/or the desired value of the control parameter.

7. The method according to claim 4, wherein the axial moment of inertia of the transmission is factored in as a function of an existing gear ratio of the transmission to be tested.

8. The method according to claim 4, wherein the measured torque of the transmission output of the transmission and/or a rotational speed of the transmission output of the transmission is measured on the test bench.

9. The method according to claim 8, wherein the measured torque of the transmission output of the transmission and/or the angular acceleration of the transmission output of the transmission is filtered by a filter, wherein the filter is selected from the group consisting of: a second-order low-pass filter, a Bessel filter, a Butterworth filter, a notch filter, or a Kalman filter.

10. The method according to claim 8, wherein the rotational speed of the transmission output of the transmission is calculated or stabilized by further measured values.

11. The method according to claim 4, further comprising at least one of the following method steps: calculating the angular acceleration of the transmission output of the transmission from a measured rotational speed of the transmission output of the transmission; and/or measuring the angular acceleration of the transmission output of the transmission.

12. The method according to claim 4, further comprising the following method step: calculating or stabilizing the measured torque of the transmission output of the transmission by means of a torque of a transmission input.

13. The method according to claim 4, wherein the measured torque of the transmission output of the transmission is determined by measuring an electrical air-gap torque of a load machine of the test bench.

14. A non-transitory computer-readable medium having instructions stored thereon, that when executed, cause to be performed the following steps: operating a transmission as a real component on a test bench for a powertrain; calculating a desired value of a control parameter of a transmission output of the transmission on a basis of a model that simulates the transmission and at least one component of an output side of the powertrain other than the transmission as virtual components, wherein the at least one component of the output side of the powertrain is not assembled on the test bench in reality but only exists as one of the virtual components and the transmission is both assembled on the test bench in reality and simulated as one of the virtual components, on a basis of at least one measurement parameter measured on the powertrain; and controlling the test bench on a basis of the desired value of the control parameter.

15. A system for controlling a test bench for a powertrain with a transmission, the system comprising: a first module for operating the transmission as a real component; a second module for calculating a desired value of a control parameter of a transmission output of the transmission on a basis of a model that simulates the transmission and at least one component of an output side of the powertrain other than the transmission as virtual components, wherein the at least one component of the output side of the powertrain is not assembled on the test bench in reality but only exists as one of the virtual components and the transmission is both assembled on the test bench in reality simulated as one of the virtual components, on a basis of at least one measurement parameter measured on the powertrain; and a third module for controlling the test bench on a basis of the desired value of the control parameter.

16. The system according to claim 15, further comprising: a fourth module for calculating an input torque of the transmission based on an axial moment of inertia of the transmission, an angular acceleration of the transmission output of the transmission, and a measured torque of the transmission output of the transmission.

17. The system according to claim 16, further comprising: a first sensor for determining the angular acceleration of the transmission output of the transmission; and a second sensor for measuring the torque of the transmission output of the transmission.

Description

(1) Further features and advantages of the invention yield from the following description based on the figures. The figures show at least in part schematically:

(2) FIG. 1 an embodiment of the inventive system installed on a test bench; and

(3) FIG. 2 a flow chart of an example embodiment of the inventive method.

(4) The inventive teaching will be described in detail on the basis of FIG. 1 which depicts an exemplary embodiment of the inventive system 20 on a transmission test bench 1 to be controlled.

(5) A real transmission 2 is mounted on the transmission test bench 1 which, as a real component of a powertrain representing the test object, is subjected to a test operation. For this task, the test bench comprises a drive unit 7, preferably an electric motor, and a load machine 6 which is preferably also designed as an electric motor.

(6) The drive unit 7 provides a torque T.sub.1 at the transmission input 5. The load machine 6 exerts a load on the transmission output 4 via a test bench shaft 8. An output which the load machine must take up as load is defined by a rotational speed n to be set at the transmission output 4, the power supplied by the drive unit 7 and the gear ratio dictated by the transmission 3.

(7) The inventive system 20 for controlling the test bench preferably comprises three modules.

(8) A first module 21 of the system 20 for controlling the test bench 1 is configured to calculate a desired rotational speed n at the transmission output 4 of the real transmission 3 mounted on the test bench 1. To that end, a preferably realtime-capable model 2 is stored in a data processing system, in particular a data storage, of the first module 21 which is able to simulate a virtual transmission 3′, a flexible shaft 15, a differential 16 as well as a vehicle axle 10a, 10b including wheels 9a, 9b as virtual components of the test object. Preferably, the simulated rest of the powertrain can also comprise fewer or additional virtual components. For example, the model can also factor in a differential 12 as a virtual component in addition to the flexible shaft 11.

(9) To calculate a desired rotational speed n to be set at the transmission output 4 on the test bench 1, information is entered into the model 2 on the operating status of the test bench 1 as determined by the measuring of a measurement parameter in relation to the powertrain 2, in particular at least one rotational speed n.sub.1, n.sub.2 and/or torque T.sub.1, T.sub.2, preferably two measurement parameters: a rotational speed n.sub.2 of the transmission output 4 of the real transmission 3 and a torque T.sub.2 of the transmission output 4 of the real transmission 3.

(10) From these two measurement parameters, a third module 23 of the system 20 calculates an input torque or an internal transmission torque T.sub.in of the transmission 3 or virtual transmission 3′ respectively, in particular in real time.

(11) This input torque T.sub.in is entered into the model 2 as an input parameter, on the basis of which the first module 21 calculates the desired rotational speed n. Preferably, the input parameter T.sub.in is thereby time-invariant, meaning it always assumes the same value given the same configuration of respective measurement parameter values.

(12) The third module 23 thereby preferably determines the input torque T.sub.in according to the following relationship:
T.sub.in=T.sub.2+J.sub.y.Math.α(t)  Equation (1)

(13) Equation (1) is in the form of a Euler differential equation solved numerically as per the invention, wherein α(t) is the angular acceleration of the transmission output 4, J.sub.y is the axial moment of inertia of the real transmission, T.sub.2 is the axial torque of the test bench shaft 8.

(14) The angular acceleration α (t) of the transmission output 4 can be determined by deriving the rotational speed n.sub.2 of the test bench shaft 8 which is connected to rotate with the transmission output 4 and the load machine 6.

(15) To that end, the system 1 preferably comprises a first sensor 24, for example an incremental encoder, configured to detect a rotation of the rotor of the load machine 6 and/or the test bench shaft 8. Alternatively, the load machine 6 can also have its own speed sensor which provides the rotational speed n.sub.2 to the third module 23 of the system 1. The rotational speed n.sub.2 can thereby be determined for example on the basis of the alternating electromagnetic field generated by the load machine 6.

(16) The following equation thereby yields the angular velocity α (t) by numerical differentiation of the rotational speed n.sub.2 at the transmission output 4:

(17) $\begin{array}{cc}\alpha \left(t\right)=\frac{n_2\left(t+\Delta t\right)-n_2\left(t\right)}{\Delta t}& \mathrm{Equation}\left(2\right)\end{array}$

(18) In order to improve the quality of the measurement signal here, e.g. a signal of the incremental encoder, different filterings can be applied to the signal in order to improve its quality. Particularly suited to this purpose are second-order low-pass filters, Bessel filters, Butterworth filters or also notch filters. Kalman filters can also be used.

(19) Additionally or alternatively, a rotational speed n.sub.1 can also be measured at the transmission input 5. From this rotational speed n.sub.1, preferably the rotational speed at the transmission output 4 can be deduced via the gear ratio of the transmission 3. The rotational speed n.sub.1 can be measured by means of a separate speed sensor 26, in particular on the load machine 6, which is connected to rotate with the transmission input 5 of the transmission 3. The sensor 26 can thereby be a component of the drive unit 7 or even an additional sensor of the inventive system 20 arranged on the load machine 7 or between the load machine 7 and the transmission input 5 in order to measure the rotational speed n.sub.1.

(20) Upon both rotational speed n.sub.1 at transmission input 5 and rotational speed n.sub.2 at transmission output 4, sensor fusion or information fusion methods can then be used in order to link the data relating to n.sub.1 and n.sub.2, potentially using the gear ratio i of the transmission if applicable, in order to improve the quality of the rotational speed signal at the transmission output 4 which is material to determining the input torque T.sub.in. In sensor fusion/information fusion, measurement signals are applicably combined so as to generate a more accurate representation of reality.

(21) Additionally possible is directly measuring the angular acceleration α (t), for example using the Ferraris principle. Given this directly measured angular acceleration α (t) and for example rotational speed n.sub.2 at the transmission output 4, as determined for example on the load machine 6, sensor fusion/information fusion methods can then also be employed here, likewise in order to improve the angular acceleration α (t) signal quality.

(22) The axial moment of inertia J.sub.y of transmission 3, 3′ preferably results from the following equation:
J.sub.y=J.sub.5.Math.i.sub.1stgear+J.sub.4  Equation (3)

(23) J.sub.5 is thereby the measured moment of inertia at transmission input 5 and J.sub.4 the measured moment of inertia of the transmission 3 at transmission output 4, each in first gear, having gear ratio i.sub.1stgear. Preferably approximated values can be used per the invention for the J.sub.4, J.sub.5 moments of inertia and the i.sub.1stgear gear ratio.

(24) The axial moment of inertia J.sub.y of the transmission 3, 3′ in first gear can thus preferably also be adopted for all the other gear ratios; i.e. assumed in approximation as a constant.

(25) The value for the axial moment of inertia J.sub.y, which is used in the third module 23, should preferably be the same as used in the first module 21 to calculate the desired rotational speed n. That means that the value used to determine the input torque T.sub.in is to preferably be identical to the value for the axial moment of inertia J.sub.y used in inventive model 2 to calculate the desired rotational speed n.

(26) The torque T.sub.2 at the transmission output 4 from equation (1) can preferably be measured by means of a torque sensor 25 on the test bench shaft 8. This measured torque T.sub.2 corresponds to the torque at the transmission output 4.

(27) The quality of the signal acquired from the torque sensor 25 can also be improved using different signal filters.

(28) Additionally, the torque T.sub.1 at the transmission input 5 can be used to calculate the value of the torque T.sub.2 at the transmission output 4, in particular utilizing gear ratio/transmission 3. It can alternatively be provided to stabilize the measurement signal of the torque T.sub.2 at the transmission output 4 by means of the torque T.sub.1 at the transmission input 5, in particular also by utilizing sensor fusion/information fusion methods.

(29) Alternatively or additionally, measurement of an air-gap torque of the load machine 6 can also be used to calculate and/or stabilize the torque T.sub.2 at the transmission output 4.

(30) The input torque T.sub.in calculated in the third module 23 is fed into the model 2 for calculating a rotational speed n at the transmission output 4, 4′. The input torque T.sub.in thereby in particular serves to factor the axial moment of inertia J.sub.y of the transmission 3, 3′ into the simulation of the rest of the powertrain's behavior.

(31) Preferably, the calculated rotational speed n is output to a second module 22 of the system 1 for controlling the test bench, in particular for controlling the load machine 6. The second module 22 can thereby be both part of the inventive system 20 as well as part of a controller already on the test bench 1.

(32) The principle described above with reference to FIG. 1 for controlling a test bench 1 is broken down into individual method steps based on FIG. 2.

(33) In order to be able to calculate an input torque T.sub.in for simulation in the model, the angular acceleration α (t) is first calculated, 101a, preferably on the basis of a measured rotational speed n.sub.2 of the transmission output 4. Alternatively or additionally, the angular acceleration α (t) is measured by suitable sensors, 101b. Additionally, a torque T.sub.2 of the transmission output is measured or calculated or additionally stabilized via the torque T.sub.1 of the transmission input 5, 101c.

(34) In a next step, the input torque T.sub.in is calculated in real time, wherein the axial moment of inertia J.sub.y of the real transmission 3, the angular acceleration α (t) and the torque T.sub.2 at the transmission output 4 of the real transmission 3 as calculated as described with reference to FIG. 1 are taken as the input parameter.

(35) The desired rotational speed n at the transmission output 4 is calculated in the model 2 using the input torque T.sub.in as well as further properties of the rest of the powertrain, preferably consisting of the shaft 11, differential 12, axle 10a, 10b and the wheels 9a, 9b, 102. The test bench 1, in particular its load machine 6, is controlled on the basis of said desired rotational speed n, 103.

(36) The described control process enables a control loop of a test bench 1 for a powertrain having a real transmission 3 and a virtual flexible shaft 11 which ensures stable operation of the test bench 1 at a rotational speed n to be set at the transmission output 4.

(37) The exemplary embodiments described in the foregoing are merely examples which in no way limit the protective scope, application or design of the invention. Rather, the preceding description affords one skilled in the art a guideline for the implementation of at least one embodiment, whereby various modifications can be made, in particular with regard to the function and configuration of the described components, without departing from the protective scope ensuing from the claims and equivalent feature combinations.

LIST OF REFERENCE NUMERALS

(38) 1 test bench 2 powertrain 3 transmission 4 transmission output 5 transmission input 6 load machine 7 drive unit 8 test bench shaft 9a, 9b wheel 10a, 10b axle section 11 shaft 12 differential 20 system 21 first module 22 second module 23 third module 24 first sensor 25 second sensor 26 third sensor 27 fourth sensor T.sub.in input torque T.sub.1 torque of transmission input T.sub.2 torque of transmission output n.sub.1 rotational speed of transmission input n.sub.2 rotational speed of transmission output α(t) angular acceleration J.sub.y axial moment of inertia J.sub.4 moment of inertia at transmission output J.sub.5 moment of inertia at transmission input