Method for determining the noise or vibration response of a vehicle subassembly and test equipment therefor

Abstract

The present application relates to a method for determining a noise or vibration response of a vehicle subassembly and a test device for the same. A method for determining a noise or vibration response of a vehicle subassembly may include: transmitting an input torque control signal to a first motor of the test device via a controller. The first motor is mountable on a test fixture of the test device and is configured to be coupled to the vehicle subassembly. The input torque control signal causes the first motor to provide an input torque characterized as a third-order derivative Gaussian function. The method also includes: receiving a response of the vehicle subassembly to the input torque; and performing a control action with respect to the vehicle subassembly based on the response via the controller.

Description

Technical Field

[0001] The present disclosure generally relates to a method for determining the noise and / or vibration response of a vehicle subassembly having torsion compliance, and a test apparatus for testing the noise or vibration response of a vehicle subassembly having torsion compliance. Background Art

[0002] Vehicle manufacturers strive to manufacture vehicles that will perform within acceptable noise, vibration and harshness standards throughout their lifetime. Vehicles, including automotive vehicles, include hundreds of individual components. Different subsets of these components may be sub-assembled with each other and / or may be manufactured by different entities prior to final assembly into the vehicle. Some vehicle subassemblies of components may have torsional compliance in that they experience some vibration or noise in response to torque input. Summary of the invention

[0003] In order to determine compliance with noise and vibration standards early in the design process, the noise, vibration and harshness characteristics of various torsionally compliant subassemblies of vehicle components must be accurately reproduced in an off-vehicle setting (such as in a laboratory test on a test rig). The present disclosure includes a method for determining the noise or vibration response of a vehicle subassembly and a test rig for testing the noise or vibration response, and a more accurate reproduction is achieved by isolating the subassembly to be tested (e.g., a subassembly of a connected component) to accurately focus on its response, and providing an input torque to the isolated subassembly that more accurately represents the in-use torque excitation that will be experienced by the subassembly when installed on an assembled vehicle. The methods and tests disclosed herein can ensure that the vibration and noise response of the vehicle subassembly is within predetermined limits.

[0004] A method for determining a noise or vibration response of a vehicle subassembly is implemented by a controller on a test device. The method may include: transmitting an input torque control signal to a first motor of the test device via the controller. The first motor can be mounted on a test fixture and is configured to be coupled to the vehicle subassembly. The input torque control signal causes the first motor to provide an input torque characterized as a third-order derivative Gaussian function. The method also includes: receiving a response of the vehicle subassembly to the input torque; and performing a control action with respect to the vehicle subassembly based on the response via the controller. As used herein, a controller may include one or more interconnected or separate controllers, and may include one or more data acquisition devices that receive and store test data. For example, a controller on the test device may include a processor that provides motor commands, and may include a data acquisition device that receives sensor signals (such as accelerometer signals) indicating the vibration response of the subassembly, and the separate controller may subsequently analyze the data received by the data acquisition device. For example, the separate controller may be remote from the fixture and motors of the test device and the controllers connected to the motors, and may analyze the data and perform one or more steps of the method disclosed herein at any time point after the stored data is received by the data acquisition device.

[0005] In one aspect, the method may include comparing the response to a predetermined threshold indicating an unacceptable level of noise or vibration. The control action may be based on whether the response equals or exceeds the predetermined threshold. For example, the predetermined threshold may be a maximum acceleration magnitude corresponding to a vibration or sound threshold. The predetermined threshold is stored on the controller, and when the controller compares the response to the predetermined threshold, performing the control action may include recording a diagnostic code if the response exceeds the predetermined threshold. In addition, performing the control action may include rejecting the vehicle subassembly during the design verification process if a diagnostic code indicating non-compliance with respect to the predetermined threshold is recorded. In the same embodiment or in other embodiments, the test equipment may include a display operatively connected to the controller, and performing the control action may include sending a display signal that causes the display to display an indicator of whether the response exceeds the predetermined threshold.

[0006] In one aspect, the test apparatus may include at least one accelerometer operatively connectable to a vehicle subassembly and a controller, such as a data acquisition (DAQ) device connected to the controller. The accelerometer may be configured to measure a response of the vehicle subassembly and output an accelerometer signal indicative of the response that may be received by the controller, such as by the DAQ.

[0007] In another aspect, the test apparatus may include a second motor that is mountable on a test fixture and configured to be coupled to a vehicle subassembly, wherein the vehicle subassembly is isolated between the first motor and the second motor. In such an embodiment, the method may further include transmitting a reaction torque control signal to the second motor via a controller. The reaction torque control signal may cause the second motor to provide an additional input torque to the vehicle subassembly, wherein the additional input torque is opposite to the input torque of the first motor. For example, the additional input torque provided by the second motor may be characterized as a torsion spring. This may represent a reaction torque on the opposite end of the vehicle subassembly when the vehicle subassembly is mounted on a vehicle and when an input torque is applied to one end of the vehicle subassembly.

[0008] In one aspect, the torque input to the tested vehicle subassembly may be in accordance with some user-controlled input. In other words, the entity implementing the test may select a relative scale of the input torque of the first motor. For example, the input torque control signal of the first motor may correspond to a selected scaling factor that indicates a desired peak torque and a desired torque application rate. The scaling factor may scale the ratio of the peak torque to the torque application rate while maintaining the third derivative Gaussian characteristics of the input torque of the first motor.

[0009] A test apparatus for testing a noise or vibration response of a vehicle subassembly may include: a test fixture; a first motor mountable on the test fixture and configured to be coupled to the vehicle subassembly; a controller configured to execute stored instructions characterizing the noise or vibration response of the vehicle subassembly, the execution of the stored instructions causing the controller to transmit an input torque control signal to the first motor, wherein the input torque control signal causes the first motor to provide an input torque characterized as a third-order derivative Gaussian function. Executing the stored instructions may include: receiving a response of the vehicle subassembly to the input torque; and executing a control action with respect to the vehicle subassembly based on the response.

[0010] The test apparatus may include at least one accelerometer operably connected to the vehicle subassembly and the controller, and the accelerometer may be configured to measure a response of the vehicle subassembly and output an accelerometer signal indicative of the response. The vehicle subassembly may include a torsional compliance feature. The accelerometer may be operably connected to the vehicle subassembly at or adjacent to the torsional compliance feature. Such a location of the accelerometer may be a point of interest given that vibration and / or noise may have a greater magnitude at the torsional compliance feature than elsewhere on the vehicle subassembly.

[0011] The test apparatus may also include a second motor mountable on the test fixture and configured to couple to the vehicle subassembly, wherein the vehicle subassembly is isolated between the first motor and the second motor. The controller may transmit a reaction torque control signal to the second motor, the reaction torque control signal causing the second motor to provide an additional input torque to the vehicle subassembly, the additional input torque being characterized as a torsion spring and opposing the input torque of the first motor, as described above.

[0012] The controller may be capable of being operably connected to an operator input feature configured to enable an operator to select a scaling factor for the input torque control signal that corresponds to a ratio of peak torque to torque application rate, the ratio corresponding to a desired peak torque and a desired torque application rate, as described above.

[0013] Thus, by using a more accurate input torque characterized as a third-order derivative Gaussian function, the performance of the controller in determining compliance with respect to noise and / or vibration criteria is improved. Similarly, the test rig is improved by utilizing a controller that provides a third-order derivative Gaussian function torque input, and isolating the vehicle subassembly between the first motor and the second motor so that the torsional compliance characteristics of the vehicle subassembly receive the accurately modeled torque input in the same manner as the vehicle subassembly will on the vehicle.

[0014] The present invention includes the following technical solutions:

[0015] Technical Solution 1. A method for determining the noise or vibration response of a vehicle subassembly on a test device, the method comprising:

[0016] transmitting an input torque control signal to a first motor of the test rig via a controller, the test rig also including the controller and a test fixture, the first motor being mountable on the test fixture and configured to be coupled to the vehicle subassembly;

[0017] wherein the input torque control signal causes the first motor to provide an input torque characterized as a third-order derivative Gaussian function;

[0018] receiving a response of the vehicle subassembly to the input torque; and

[0019] A control action is performed, via the controller, with respect to the vehicle subassembly based on the response.

[0020] Technical Solution 2. The method according to Technical Solution 1 further comprises:

[0021] comparing the response to a predetermined threshold value indicative of an unacceptable level of noise or vibration; and

[0022] Wherein, the control action is based on whether the response is equal to or exceeds the predetermined threshold.

[0023] Technical Solution 3. The method according to Technical Solution 2, wherein the predetermined threshold is the magnitude of acceleration.

[0024] Technical Solution 4. The method according to Technical Solution 2, wherein executing the control action includes: recording a diagnostic code if the response exceeds the predetermined threshold.

[0025] Technical Solution 5. The method according to Technical Solution 4, wherein executing the control action includes: if the diagnostic code is recorded, rejecting the vehicle sub-assembly during the design verification process.

[0026] Technical Solution 6. The method according to Technical Solution 2, wherein:

[0027] The test device includes a display operatively connectable to the controller; and

[0028] Performing the control action includes sending a display signal to the display, the display signal causing the display to display an indicator on the display of whether the response exceeds the predetermined threshold.

[0029] Technical Solution 7. The method according to Technical Solution 1, wherein:

[0030] The test apparatus includes at least one accelerometer operatively connectable to the vehicle subassembly and the controller;

[0031] the accelerometer being configured to measure the response of the vehicle subassembly and output an accelerometer signal indicative of the response; and

[0032] Receiving the response of the vehicle subassembly to the input torque includes receiving the accelerometer signal.

[0033] Technical Solution 8. The method according to Technical Solution 1, wherein the test device includes a second motor that can be mounted on the test fixture and is configured to be coupled to the vehicle subassembly, wherein the vehicle subassembly is isolated between the first motor and the second motor, and the method further includes:

[0034] A reactive torque control signal is transmitted via the controller to the second motor; wherein the reactive torque control signal causes the second motor to provide an additional input torque to the vehicle subassembly that is opposite to the input torque of the first motor.

[0035] Technical Solution 9. The method according to Technical Solution 8, wherein the additional input torque provided by the second motor is characterized as a torsion spring.

[0036] Technical Solution 10. The method according to Technical Solution 9, wherein the second motor includes a rod, through which the additional input torque is provided, and the rod has a selected spring stiffness.

[0037] Technical Solution 11. The method according to Technical Solution 1, wherein the input torque control signal corresponds to a selected scaling factor, and the selected scaling factor indicates a desired peak torque and a desired torque application rate.

[0038] Technical Solution 12. A test device for testing the noise or vibration response of a vehicle subassembly, the test device comprising:

[0039] Testing fixtures;

[0040] a first motor mountable on the test fixture and configured to be coupled to the vehicle subassembly;

[0041] a controller configured to execute stored instructions characterizing a noise or vibration response of the vehicle subassembly, execution of the stored instructions causing the controller to:

[0042] transmitting an input torque control signal to the first motor; wherein the input torque control signal causes the first motor to provide an input torque characterized as a third-order derivative Gaussian function;

[0043] receiving a response of the vehicle subassembly to the input torque; and

[0044] A control action is performed with respect to the vehicle subassembly based on the response.

[0045] Technical Solution 13. The testing device according to Technical Solution 12, wherein:

[0046] Execution of the stored instructions further causes the controller to compare the response to a predetermined threshold value indicative of an unacceptable level of noise or vibration; and

[0047] Performing the control action includes logging a diagnostic code if the response equals or exceeds the predetermined threshold.

[0048] Technical Solution 14. The test device according to Technical Solution 13, wherein executing the control action includes: if the diagnostic code is recorded, rejecting the vehicle sub-assembly during the design verification process.

[0049] Technical Solution 15. The testing device according to Technical Solution 13, wherein:

[0050] The testing device includes a display operatively connected to the controller; and

[0051] Performing the control action includes comparing the response to a predetermined threshold indicating an unacceptable level of noise or vibration and sending a display signal that causes the display to display an indicator of whether the response exceeds the predetermined threshold.

[0052] Technical Solution 16. The testing device according to Technical Solution 12 further comprises:

[0053] at least one accelerometer operatively connectable to the vehicle subassembly and the controller;

[0054] wherein the accelerometer is configured to measure the response of the vehicle subassembly and output an accelerometer signal indicative of the response; and

[0055] Wherein receiving the response of the vehicle subassembly to the input torque includes receiving the accelerometer signal.

[0056] Technical Solution 17. The testing device according to Technical Solution 16, wherein:

[0057] The vehicle subassembly includes a torsional compliance feature; and

[0058] The at least one accelerometer is operatively connectable to the vehicle subassembly at or adjacent the torsional compliance feature.

[0059] Technical Solution 18. The testing device according to Technical Solution 12 further comprises:

[0060] a second motor mountable on the test fixture and configured to be coupled to the vehicle subassembly, wherein the vehicle subassembly is isolated between the first motor and the second motor; and

[0061] Wherein, executing the stored instructions further causes the controller to transmit a reaction torque control signal to the second motor; wherein the reaction torque control signal causes the second motor to provide additional input torque to the vehicle subassembly, the additional input torque being opposite to the input torque of the first motor.

[0062] Technical Solution 19. The testing device according to Technical Solution 18, wherein the additional input torque provided by the second motor is characterized as a torsion spring.

[0063] Technical Solution 20. A test device according to Technical Solution 12, wherein the test device has an operator input feature, which is operatively connected to the controller and is configured to enable an operator to select a scaling factor for the input torque control signal, the scaling factor corresponding to the desired peak torque and torque application rate.

[0064] The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings as defined in the appended claims when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The drawings described herein are for illustrative purposes only, are schematic in nature, and are intended to be exemplary rather than limiting the scope of the present disclosure.

[0066] Figure 1 is a schematic illustration of a test rig and a vehicle subassembly secured to the test rig for determining the noise and / or vibration response of the vehicle subassembly.

[0067] Figure 2 yes Figure 1 Schematic illustration of a test rig to which different vehicle subassemblies are secured for determining the noise and / or vibration response of the vehicle subassemblies.

[0068] Figure 3 is an example graph of torque input from a test rig to a vehicle subassembly showing torque on the vertical axis and time on the horizontal axis.

[0069] Figure 4 It is shown as Figure 1 and Figure 2 Flowchart of an example method for determining the noise and / or vibration response of a vehicle subassembly implemented by a test apparatus. DETAILED DESCRIPTION

[0070] Referring to the drawings, wherein like reference numerals refer to like parts throughout the several views, Figure 1A test rig 10 is shown, wherein a vehicle subassembly 12 is coupled to the test rig 10 in preparation for determining the noise and / or vibration response of the vehicle subassembly 12. The test rig 10 includes a controller 14 that is programmed to execute a set of stored instructions that embody a method 100 of inducing noise and / or vibration of the vehicle subassembly 12. As discussed herein, the test rig 10 enables the vehicle subassembly 12 to be isolated, and the torque input to the vehicle subassembly 12 commanded by the controller 14 according to the method 100 enables the noise or vibration response of the vehicle subassembly 12 to accurately represent the response of the vehicle subassembly 12 as if installed on a complete vehicle. In this manner, bench level testing (e.g., testing of the vehicle subassembly 12 on the test rig 10) can be performed to determine compliance with respect to design thresholds, thereby enabling design revisions to the vehicle subassembly 12 to be completed early in the vehicle production process. For example, testing can occur at any time even before or after any complete vehicle (on which a similar vehicle subassembly is installed) is manufactured.

[0071] Although schematically depicted as a single controller, the controller 14 may be implemented as one controller, or as a system of multiple controllers cooperating to jointly manage the test equipment 10 and analyze data retrieved from the test equipment indicating the vibration response of the vehicle subassembly under test. The multiple controllers may communicate via a serial bus (e.g., a controller area network (CAN)), via discrete conductors, or wirelessly. One or more of these controllers may be physically separate and remote from the test equipment and may implement a portion of the method related to evaluating the test data to determine whether the response of the vehicle subassembly under test is within predetermined vibration or noise limits and executing such a determined control action (e.g., providing an indicator). For example, the controller 14 includes one or more digital computers, each having a microprocessor or central processing unit (CPU) (referred to herein as processor 16) and memory 18, such as read-only memory (ROM), random access memory (RAM), electrically programmable read-only memory (EPROM), a high-speed clock, analog-to-digital (A / D) and digital-to-analog (D / A) circuits, input / output circuits and devices (I / O), and appropriate signal conditioning and buffering circuits. The one or more processors 16 may include stored computer-executable instructions of the method 100 (e.g., these instructions may be on the same processor of a single controller, or some instructions may be on a processor of one controller and other instructions may be on a processor of another controller), and these instructions, when executed, cause the controller 14 to perform actions and issue commands according to the method 100 disclosed in the present disclosure, the commands controlling the test apparatus 10 and providing an indicator of whether the vibration response of the vehicle subassembly is within predetermined limits.

[0072] In addition to the controller 14, the test apparatus 10 may include the following components, each of which is operatively connected to the controller 14, as further described herein: a first motor (M1) 20, a second motor (M2) 22, a display 24, an operator input feature 26, and one or more accelerometers 28 for measuring acceleration indicative of vibration and / or sound. For example, the display 24 is depicted as an electronic screen, and the operator input feature 26 is depicted as an electronic keyboard. For example, the display 24 and the operator input feature 26 may be operatively mounted to the fixture 30, may rest on a table (not shown), or may be embodied in a portable laptop computer. The controller 14 or portions thereof may also be integrally included in a laptop computer with the display 24 and the operator input feature 26, or may be separate therefrom. For example, the one or more accelerometers 28 may provide accelerometer signals to a data acquisition device (DAQ) 71 that may be operatively connected to the controller 14. For example, any such controller 14 included on a laptop computer may record data received from DAQ 71 and may also process the data according to method 100, or the recorded data may be transferred to another controller in one or more controllers 14 of a different computing device. Figure 1 1 and 2. Although shown as being operatively connected via transfer conductors (eg, wires), the operative connection between the controller 14 and the first motor (M1) 20, the second motor (M2) 22, the display 24, the operator input features 26, and the one or more accelerometers 28 may be wireless.

[0073] The test apparatus 10 also includes a fixture 30, which may be a fixed base or platform. The respective housing 32 of each of the first motor 20 and the second motor 22 may be fixedly mounted directly or indirectly to the fixture 30 so that the motors 20, 22 are spaced apart from each other. For example, the housing 32 may be bolted to the fixture 30, which has sufficient rigidity to isolate vibrations caused during testing of the vehicle subassembly 12 or 12A being tested. As shown, each motor 20, 22 includes a motor controller (MC) 34, which is operatively connected to the controller 14 and is configured to receive control signals from the controller 14 to control the operation of the motor. For example, the first motor 20 receives an input torque control signal 33 that causes an input torque Ƭ1 as described herein, and the second motor 22 receives a reaction torque control signal 35 that causes an input torque Ƭ2 as described herein as a reaction torque, which is configured to hold the rotor 38 of the second motor 22 (and thus one end of the subassembly 12 or 12A connected thereto) to an initial position. For example, in testing a vehicle subassembly such as a steering column electric power steering assembly, input torque Ƭ1 represents the torque applied to the steering column electric power steering assembly by other vehicle components, such as due to road loads, and input torque Ƭ2 represents the torque required to maintain the steering wheel of the steering column electric power steering assembly in a given position regardless of input torque Ƭ1.

[0074] Each motor 20, 22 is depicted as having an annular stator 36 that surrounds a rotor 38 and causes the rotor 38 to rotate about an axis of rotation (A) 40 at a rotational speed and apply a torque commanded by the controller 14. In the illustrated embodiment, the respective axes of rotation 40 of each of the motors 20, 22 are shown as being coaxial. In other arrangements, the respective axes of rotation 40 may be arranged as non-coaxial and may be parallel or otherwise disposed in a manner that allows the vehicle subassembly 12 to be operatively secured to each of the motors 20, 22 and extend therebetween, with the torque applied by the first motor 20 being in an opposite direction to the torque applied by the second motor 22.

[0075] As shown, the rotor hub 42 of each of the motors 20, 22 includes a coupling device 44, such as a clamp that is fixed to the vehicle subassembly 12. More specifically, a first location (such as a first end 46 of the vehicle subassembly 12) is fixed to the rotor 38 of the first motor 20 by the coupling device 44, and a second location (such as a second end 48 of the vehicle subassembly 12) spaced apart from the first location is fixed to the rotor 38 of the second motor 22 by the coupling device 44. With this configuration, the vehicle subassembly 12 extends between the first motor 20 and the second motor 22. Each coupling device 44 is configured to prevent the vehicle subassembly 12 from slipping or otherwise rotating relative to the corresponding rotor 38 at the coupling device 44. As shown, the second end 48 is splined (e.g., having splines 48A). When installed on the vehicle, the steering wheel will be installed at the splines 48A. Thus, the response of the vehicle subassembly 12 will be responsive only to the magnitude, direction and frequency of the torque input from the motors 20, 22, and will be caused to occur at the torsional compliance feature(s) of the vehicle subassembly 12 between the two coupling devices 44. In some cases, the length and width of the coupling device 44 are adjustable or expandable to enable coupling to a wide range of different vehicle subassemblies 12. In some cases, the vehicle subassembly 12 may be rotatably or non-rotatably supported between the first motor 20 and the second motor 22, such as at bearings or supports that extend from the fixture 30 and represent other vehicle structures to which the vehicle subassembly 12 is connected when the vehicle subassembly 12 is installed on the vehicle. Two such supports 45 are shown, extending to be threadedly connected to T-nuts 47 seated in slots 49 of the fixture 30 and bolted to the shaft 56 and steering column housing 52 described herein with bolts 51, because these are the locations where the subassembly 12 will be coupled to other vehicle structures when the subassembly 12 is installed in the vehicle. Such supports help accurately represent the on-board torsional response of the vehicle subassembly 12 when the vehicle subassembly 12 is subjected to a torque input, such as from either of the motors 20 , 22 .

[0076] Vehicle subassembly 12 Figure 1 is depicted as a steering column electric power steering assembly and may be referred to as such herein. However, it should be understood that a wide range of vehicle subassemblies that experience at least some torsional compliance may be tested on the test equipment. As used herein, a vehicle subassembly may include an assembly of multiple interconnected components. For example, certain vehicle components may be assembled (e.g., interconnected) to each other for ultimate final assembly into other components in a vehicle during vehicle manufacturing. The steering column electric power steering assembly shown as vehicle subassembly 12 is one such example. The power steering assembly may include, for example, a steering column housing 52, a worm gear 53, an assist motor 55, a shaft 56 and a housing 58 through which the shaft 56 extends, and other components. In Figure 2 An alternative vehicle subassembly 12A of the motors 20, 22 shown in FIG. 1 as being secured to the same test rig 10 is an example of an intermediate shaft having two shaft portions 56A, 56B connected via a joint 57, such as a U-joint or a constant velocity joint. In either case, such an assembly of vehicle components may be evaluated on the test rig 10 for noise and / or vibration response resulting from its torsional compliance.

[0077] To measure the response of the vehicle subassembly 12 or 12A, one or more accelerometers 28 are positioned on the vehicle subassembly 12 or 12A at or near a torsional compliance feature that is a point of interest, since such a feature is where noise or vibration is most likely to occur. For example, for a vehicle subassembly 12 that includes multiple interconnected components, the accelerometer 28 may be positioned at or near a torsional compliance feature 29, such as a coupling that couples two adjacent components to each other, whether such coupling is a flange, a fastener, a gear mesh, etc., since such a coupling may have some torsional compliance. One such torsional compliance feature 29 and accelerometer 28 is shown, wherein a shaft 56 interfaces with a housing 52. An additional torsional compliance feature is a worm gear 53, and an additional accelerometer 28 is mounted on the worm gear 53. It should be understood that additional accelerometers 28 may be placed at or near other torsional compliance features of the vehicle subassembly 12. For the vehicle subassembly 12A, for example, one or more accelerometers 28 may be placed near the joint 57 connecting the shaft portions 56A, 56B.

[0078] Figure 3 A torque input (Ƭ1) 60 is represented, which is applied to the vehicle subassembly 12 by the first motor 20 to induce a noise or vibration response and is characterized as a third-order derivative Gaussian function. When the amplitude (e.g., in Newton-meters) of the torque input of the first torque input Ƭ1 of the first motor 20 over time (e.g., in seconds) is a third-order derivative Gaussian function waveform as set forth in the following equation 1 (EQN1), the response on the test apparatus 10 best replicates the response to an on-vehicle torque input (e.g., torque applied by other vehicle components to which the vehicle subassembly 12 is ultimately connected when the vehicle subassembly 12 is installed in a vehicle, or torque applied due to road input):

[0079] EQN. 1

[0080] In EQN 1, t Indicates time, σ represents the internal scaling factor, and GRepresents a Gaussian function (e.g., a symmetrical bell-shaped curve). A third-order derivative Gaussian function input torque wave has the following: an initial relatively small amplitude peak torque (p) in a positive rotational direction (e.g., clockwise); followed by a relatively large amplitude (maximum amplitude) peak torque (-P) in a negative rotational direction (e.g., counterclockwise); followed by a maximum amplitude peak torque (P) in the positive rotational direction, which is equal in magnitude but opposite in direction to the peak torque -P; and then followed by a relatively small amplitude peak torque (-p) that is equal in magnitude but opposite in direction to the relatively small peak torque (p).

[0081] Under some embodiments of method 100 , the absolute value of the peak torque (P) (eg, the maximum amplitude of the torque input Ƭ1) and the internal scaling factor of the Gaussian function G may be selected by an operator running a test on the vehicle subassembly 12 using the test apparatus 10 σ Internal scaling factor σ The selection of changes the ratio of the resulting amplitude to the wavelength of the resulting sub-wave, which serves as a scaling factor of the amplitude (e.g., peak torque P) to the wavelength (λ). For example, an operator of the test apparatus 10 may use the operator input feature 26 to input or select the peak torque (P) and the internal scaling factor σ The value of . Figure 3 The internal scaling factor selected when the torque input is 60 is shown in σ The internal scaling factor is selected compared to the value of σ A relatively low value of will result in a torque input with a shorter wavelength (e.g., where the wave is compressed in the horizontal direction, so that t 1 and - t 1 relative to its Figure 3 closer to each other on the graph), and thus increase the torque application rate. Figure 3 The internal scaling factor selected when the torque input is 60 is shown in σ The internal scaling factor is selected compared to the value of σ A relatively high value of will result in a torque input with a longer wavelength and a lower torque application rate (e.g., where the wave is elongated in the horizontal direction so that t 1 and - t 1 relative to its Figure 3 are further apart on the graph). For example, in the basic equation, the internal scaling factor σ Can be selected to have a value of 1 and adjust the rate of application by changing the time scale. Internal Scaling Factor σ May not have the value zero.

[0082] A reaction torque (Ƭ2) 62 (described herein) opposing the third-order derivative Gaussian function input torque 60 is applied to another location on the vehicle subassembly 12 by the second motor 22. When the vehicle subassembly 12 is ultimately assembled within the vehicle, the reaction torque experienced by the vehicle subassembly 12 is best represented as a torsion spring having a torque in a direction opposite to the direction of the third-order derivative Gaussian torque input Ƭ1. Accordingly, the controller 14 is configured to transmit a reaction torque control signal 35 to the second motor 22 that causes the second motor 22 to apply an additional input torque Ƭ2 (e.g., the second torque input Ƭ2 of the second motor 22) to the vehicle subassembly 12 as a reaction torque in a rotational direction opposite to the rotational direction of the input torque of the first motor 20. The input torque Ƭ2 applied by the second motor 22 has a magnitude (e.g., in Newton-meters) that increases with angular rotation according to the formula for a torsion spring in Equation 2 (EQN. 2) as follows:

[0083] EQN. 2

[0084] In EQN. 2, k is the spring constant, and θ is the angle at which the vehicle subassembly 12 is twisted from its equilibrium position, as may be determined by an accelerometer 28 disposed at or near a torsional compliance feature, such as the linkage 44 .

[0085] With the vehicle subassembly 12 clamped or otherwise secured between and extending between the two motors 20, 22, one or more torsional compliance features of the vehicle subassembly 12 are located between the two torque inputs, and the noise and vibration induced in the vehicle subassembly 12 by the first torque input Ƭ1 and the second torque input Ƭ2 at the torsional compliance features accurately represent what occurs when the vehicle subassembly 12 is mounted on a vehicle. The one or more accelerometers 28 output an accelerometer signal 70 to the controller 14 that is indicative of the noise and / or vibration response of the vehicle subassembly 12 (e.g., its acceleration) to the input torque Ƭ1.

[0086] Figure 41 is a flow chart representing a method 100 for determining a noise or vibration response of a vehicle subassembly 12, 12A, etc., as implemented by the controller 14, with the vehicle subassembly 12 on the test rig 10. As discussed herein, the controller 14 may include multiple controllers, and different portions (e.g., steps) of the method 100 may be implemented by different ones of the controllers. The method 100 may begin at step 102 by transmitting an input torque control signal 33 to a first motor 20 of the test rig 10 via the controller 14 to apply an input torque Ƭ1 as a third-order derivative Gaussian function as described herein. The applied input torque Ƭ1 may correspond to an operator-selected torque application rate and an internal scaling factor indicating a desired peak torque and a desired torque application rate as described herein, such as may be input by an operator using the operator input feature 26.

[0087] Concurrently with step 102, method 100 may include step 104: transmitting a reaction torque control signal 35 to the second motor 22 via the controller 14 to apply an input torque Ƭ2 as a torsion spring reaction torque as described herein. The applied input torque Ƭ2 may be related to an operator selected spring stiffness as described herein. k Correspondingly, such as may be input by an operator using the operator input feature 26, or such as may be calculated by the controller 14 based on the applied input torque Ƭ1. Alternatively or in addition, a physical rod 39 may be included in the second motor 22 (e.g., such as a portion of the rotor hub 42), the spring rate of which changes when torque is applied. In an example where the vehicle subassembly 12 is a steering column electric steering column assembly, the spring rate of the physical rod 39 may represent the torque that the driver would apply in order to keep a steering wheel included in or attached to the steering column electric steering column assembly in the center (e.g., not rotating).

[0088] In step 106 of method 100, controller 14 may receive a response of vehicle subassembly 12 to input torques Ƭ1 and Ƭ2, such as by receiving one or more accelerometer signals 70 output to controller 14 from one or more accelerometers 28. In some examples, controller 14 may receive accelerometer signals 70 indirectly as recorded data provided by DAQ 71 that directly receives accelerometer signals 70.

[0089] In step 108, based on the accelerometer signal 70 (which indicates both vibration and noise experienced by the vehicle subassembly 12 at the torsional compliance feature), the method 100 can compare the response of the vehicle subassembly 12 to a predetermined threshold indicating an unacceptable level of noise or vibration. For example, the vibration as indicated by the accelerometer signal 70 can be compared to a predetermined threshold of the maximum acceleration magnitude caused by the input torque. Similarly, the accelerometer signal 70 may indicate vibration of the vehicle subassembly 12 along gravity (g) at the torsional compliance feature 29 in response to the torque input Ƭ1, and can be compared by the controller 14 to a predetermined threshold of the maximum vibration magnitude (e.g., rattle) caused by the input torque.

[0090] If it is determined in step 108 that the response of the vehicle subassembly 12 exceeds a predetermined threshold, the method 100 may move to step 110 and perform a control action. This control action need not be performed on the vehicle subassembly 12 or 12A in the test setting, but may instead be a control action performed for diagnostic purposes. For example, the control action may include logging a diagnostic code or otherwise indicating when the response exceeds a predetermined threshold. In addition, performing the control action in step 110 may include rejecting the vehicle subassembly 12 during the design verification process when a diagnostic code or other indicator is logged or otherwise indicated that the vehicle subassembly 12 does not meet the predetermined threshold criteria. In other words, the diagnostic code may be a code for rejecting the subassembly 12. Alternatively or in addition, performing the control action in step 110 may include the controller 14 sending a display signal 72 (see Figure 1 ), which displays a signal that causes the display 24 to display an indicator of whether the response exceeds a predetermined threshold. For example, if the response of the vehicle subassembly 12 exceeds the predetermined threshold, the control action of step 110 may be a diagnostic code or other alarm displayed on the display 24 indicating that the vehicle subassembly 12 does not meet the predetermined vibration or noise limits. If it is determined in step 108 that the vibration and noise response of the vehicle subassembly 12 to the input torques Ƭ1 and Ƭ2 is within acceptable limits (e.g., less than the predetermined threshold), the method may move to step 112, where a control action is performed by the controller 14, such as generating a logged diagnostic code or display content shown, which indicates that the noise and vibration response of the subassembly 12 "passes" the test implemented on the test device 10, such as the response is less than the predetermined noise and vibration threshold. As previously discussed, such control actions may occur in real time during the test, or may occur later after analyzing stored test data, such as on a remote controller 14 that is separate from the controller 14 that controls the motors 20 and 22.

[0091] The detailed description and the accompanying drawings or figures are supportive and depict the present teaching, but the scope of the present teaching is limited only by the claims. Although some of the best modes and other embodiments for implementing the present teaching have been described in detail, there are various alternative designs and embodiments for practicing the present teaching defined in the appended claims.

Claims

1. A method of determining the noise or vibration response of a vehicle subassembly on a test device, the method comprising: include: transmitting an input torque control signal to a first motor of the test rig via a controller, the test rig also including the controller and a test fixture, the first motor being mountable on the test fixture and configured to be coupled to the vehicle subassembly; wherein the input torque control signal causes the first motor to provide an input torque characterized as a third-order derivative Gaussian function, the input torque being provided to the vehicle subassembly to cause the vehicle subassembly to twist; receiving a response of the vehicle subassembly to the input torque; and A control action is performed, via the controller, with respect to the vehicle subassembly based on the response.

2. The method according to claim 1, further comprising: include: comparing the response to a predetermined threshold value indicative of an unacceptable level of noise or vibration; as well as Wherein, the control action is based on whether the response is equal to or exceeds the predetermined threshold.

3. The method according to claim 2, in, The predetermined threshold is the magnitude of acceleration.

4. The method according to claim 2, in, Performing the control action includes logging a diagnostic code if the response exceeds the predetermined threshold.

5. The method according to claim 4, in, Performing the control action includes rejecting the vehicle subassembly during a design verification process if the diagnostic code is logged.

6. The method according to claim 2, in: The test device includes a display operatively connectable to the controller; and Performing the control action includes sending a display signal to the display, the display signal causing the display to display an indicator on the display of whether the response exceeds the predetermined threshold.

7. The method according to claim 1, in: The test apparatus includes at least one accelerometer operatively connectable to the vehicle subassembly and the controller; the accelerometer being configured to measure the response of the vehicle subassembly and output an accelerometer signal indicative of the response; as well as Receiving the response of the vehicle subassembly to the input torque includes receiving the accelerometer signal.

8. The method according to claim 1, in, The test apparatus includes a second motor mountable on the test fixture and configured to be coupled to the vehicle subassembly, wherein the vehicle subassembly is isolated between the first motor and the second motor, and the method further includes: A reactive torque control signal is transmitted via the controller to the second motor; wherein the reactive torque control signal causes the second motor to provide an additional input torque to the vehicle subassembly that is opposite to the input torque of the first motor.

9. The method according to claim 8, in, The additional input torque provided by the second motor is characterized as a torsion spring.

10. The method according to claim 9, in, The second motor includes a rod through which the additional input torque is provided, the rod having a selected spring rate.

11. The method according to claim 1, in, The input torque control signal corresponds to a selected scaling factor that is indicative of a desired peak torque and a desired torque-application rate.

12. A test apparatus for testing the noise or vibration response of a vehicle subassembly, the test apparatus include: Testing fixtures; a first motor mountable on the test fixture and configured to be coupled to the vehicle subassembly; a controller configured to execute stored instructions characterizing a noise or vibration response of the vehicle subassembly, execution of the stored instructions causing the controller to: transmitting an input torque control signal to the first motor; wherein the input torque control signal causes the first motor to provide an input torque characterized as a third-order derivative Gaussian function, the input torque being provided to the vehicle subassembly to cause the vehicle subassembly to twist; receiving a response of the vehicle subassembly to the input torque; and A control action is performed with respect to the vehicle subassembly based on the response.

13. The test device according to claim 12, in: Execution of the stored instructions further causes the controller to compare the response to a predetermined threshold value indicative of an unacceptable level of noise or vibration; as well as Performing the control action includes logging a diagnostic code if the response equals or exceeds the predetermined threshold.

14. The test device according to claim 13, in, Performing the control action includes rejecting the vehicle subassembly during a design verification process if the diagnostic code is logged.

15. The test device according to claim 13, in: The test device includes a display operatively connected to the controller; and Performing the control action includes: comparing the response to a predetermined threshold value indicative of an unacceptable level of noise or vibration; and sending a display signal, the display signal causing the display to display an indicator of whether the response exceeds the predetermined threshold.

16. The test device according to claim 12, further comprising: include: at least one accelerometer operatively connectable to the vehicle subassembly and the controller; wherein the accelerometer is configured to measure the response of the vehicle subassembly and output an accelerometer signal indicative of the response; and Wherein receiving the response of the vehicle subassembly to the input torque includes receiving the accelerometer signal.

17. The test device according to claim 16, in: The vehicle subassembly includes a torsional compliance feature; and The at least one accelerometer is operatively connectable to the vehicle subassembly at or adjacent the torsional compliance feature.

18. The test device according to claim 12, further comprising: include: a second motor mountable on the test fixture and configured to be coupled to the vehicle subassembly, wherein the vehicle subassembly is isolated between the first motor and the second motor; and Wherein, executing the stored instructions further causes the controller to transmit a reaction torque control signal to the second motor; wherein the reaction torque control signal causes the second motor to provide additional input torque to the vehicle subassembly, the additional input torque being opposite to the input torque of the first motor.

19. The test device according to claim 18, in, The additional input torque provided by the second motor is characterized as a torsion spring.

20. The test device according to claim 12, in, The test apparatus has an operator input feature operatively connected to the controller and configured to enable an operator to select a scaling factor for the input torque control signal, the scaling factor corresponding to a desired peak torque and torque application rate.

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