Abstract:
A 6-axis road simulator test system is disclosed which allows for dynamic simulation of vehicles on road surfaces in a controlled environment for development or production testing conditions. The system turns the vehicle wheels, or provides resistance to turning of the wheels while subjecting each of the vehicle&#39;s wheel in up to 6-axis of displacement, based on road profile simulation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part application of pending PCT International Application PCT/IB03/02372 which was filed in the U.S. Receiving Office designating the United States on May 14, 2003, and published on Nov. 20, 2003 as WO 03/095966 A2. PCT International Application PCT/IB03/02372 claims the benefit of U.S. Provisional Application No. 60/380,401, filed May 14, 2002. The disclosure of the above applications is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a vehicle test simulator, and more particularly to a flat road simulator for a land vehicle.  
       BACKGROUND OF THE INVENTION  
       [0003]     Heretofore, methods for simulating an effective road profile in the testing of an automotive vehicle typically relied on a spindle-coupled road simulator. Spindle-coupled road simulators typically define a flat surface road plane in a multiple coordinate reference system to represent an effective road profile. These simulators often couple shakers and vertical actuators directly to the spindle of the vehicle. The spindle is excited over a predetermined range of motion to simulate the road. As spindle coupled actuators neglect the effects of tire loading on vehicle dynamics, they often are not effective in the simulation of certain driving conditions.  
         [0004]     Another commonly used vehicle test apparatus includes an articulated running flat belt platform moveable so as to contact the tire, the flat tire contact plane defines a coordinate reference system to represent the effective road profile. It is known to apply actuating forces in a vertical direction to simulate road conditions. The use of these vertical forces does not, however, completely simulate extreme driving conditions.  
         [0005]     While the above recited systems represent a significant advance in the vehicle simulation art, further advances are needed to overcome the above described problems.  
       SUMMARY OF THE INVENTION  
       [0006]     A 6-axis road simulator test system is disclosed which allows for dynamic simulation of vehicles on road surfaces in a controlled environment for development or production testing conditions. The system turns the vehicle wheels, or provides resistance to turning of the wheels while subjecting each of the vehicle wheels in up to 6-Axis of displacement, based on road profile simulation or user.  
         [0007]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0009]      FIG. 1  discloses a perspective view of the road simulator according to an embodiment of the present invention;  
         [0010]      FIG. 2  shows a perspective view of a single road simulator actuator according to the teachings of the present invention;  
         [0011]      FIG. 3  depicts the definition of the 6-axis of freedom afforded by the road simulator shown in  FIG. 2 ;  
         [0012]      FIG. 4  depicts a front perspective view of the actuator shown in  FIG. 2 ;  
         [0013]      FIG. 5  is a top perspective view of the actuator shown in  FIG. 2 ;  
         [0014]      FIG. 6  is a view of the control console coupled to the actuator in  FIG. 2 ;  
         [0015]      FIGS. 7-9  are rear perspective views of the actuator shown in  FIG. 2 ;  
         [0016]      FIG. 10  is a top view of the actuator shown in  FIG. 2 ;  
         [0017]      FIG. 11  is an internal view of the simulator shown in  FIG. 2 ;  
         [0018]      FIGS. 12-14  are a close-up view of the hydraulic actuators with closed loop controls;  
         [0019]      FIGS. 15 and 16  are depictions of the suspension arm;  
         [0020]      FIG. 17  is a depiction of a remote control device coupled to the controller;  
         [0021]      FIG. 18  depicts a rear perspective view of the system according to the teachings of the present invention;  
         [0022]      FIG. 19  depicts a side view of the system shown in  FIG. 18 ;  
         [0023]      FIG. 20  shows a top view of the system shown in  FIG. 18 ;  
         [0024]      FIG. 21  represents a superstructure of the simulator according to the teachings of the present invention;  
         [0025]      FIG. 22  depicts a base structure according to the teachings of the present invention;  
         [0026]      FIGS. 23-26  represent rear perspective views of the simulator shown in  FIG. 18 ;  
         [0027]      FIG. 27  depicts a rear view of the actuator superstructure;  
         [0028]      FIG. 28  represents a front perspective view of the simulator according to the teachings of an additional embodiment of the invention;  
         [0029]      FIG. 29  represents a rear perspective view of the simulator shown in  FIG. 28 ; and  
         [0030]      FIGS. 30 and 31  represent top and front views of the simulators shown in  FIG. 28 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. With general reference to  FIGS. 1-26  and particular reference to  FIG. 1  which discloses a perspective view of the road simulator  50  according to an embodiment of the present invention. The road simulator  50  is configured to simulate a road for a vehicle by inputting a simulation of a road into a vehicle&#39;s tires. Testing provided by the system can include, but is not limited to, vehicle dynamics, NVH (noise, vibration, and handling), rigidity, natural frequency of vehicle and suspension, etc. Production testing can include end-of-line testing of vehicle driving and/or braking functions.  
         [0032]     These simulations are accomplished by the use of four individually controlled actuators (one per tire as needed). Each actuator is configured to use individual closed loop controls to vary the vehicle tire speed, and displacement of the tires with 6-axis of displacement. If desired, a single or pair of road simulators can be used to test vehicle sub-assemblies such as tires, wheels, an individual axle, suspension assembly, or a complete vehicle.  
         [0033]     All displacement and speed drives are integrated into the actuators. The input signal simulating the road can be computer generated or can be taken from acceleration data from inside an exemplary vehicle traveling down the test road. Examples of this data include data from the vehicle interior, suspension data, tire data, etc. Any of the above input data is mathematically correlated to an actual road profile.  
         [0034]     Each of the individual actuators has an associated water cooled drive motor  52  for quiet operation that is coupled to a drive shaft by a flexible coupling  54 . The flexible coupling  54  is preferably an extensible constant velocity joint that allows the motor  52  to be mounted to the base  56  of the system, while the actuator is suspended on a support member. Additionally, each actuator has a driven belt  58  for either driving or resisting the rotation of the vehicle&#39;s tires. The driven belt  59  (as detailed herein) is supported by two to four drums  60  and a bearing  62  disposed immediately below the belt  58  wheel interface. The bearing is optionally hydrostatic and can be a high pressure air-bearing (25 to 30 bar). The drums and belt can be steel or some other material such as a reinforced polymer.  
         [0035]      FIG. 2  shows a perspective view a single road simulator actuator  50  according to the teachings of the present invention. The road simulator  50  contains closed loop controls of a vehicle&#39;s tire speed, traction control and braking force on the belt, as well as up to 6-axis of displacement. These feedback controls can be incorporated into the system controller, or can be incorporated directly into the individual actuators. The test system utilizes a controller which contains electrical/electronics, data acquisition system, and software. The controller is accessible through typical networking means such as Ethernet and functions to individually control each of the actuators.  
         [0036]     The controller  61  utilizes sensors to measure the speed of the driven belt and/or the vehicles wheel. In measuring the rotational velocity of the wheel or the belt, it is envisioned that sensors such as magnetorestrictive, optical, magnetic, and capacity sensors can be used. Additionally, where available, the system can utilize data from the test vehicle&#39;s anti-lock braking system or traction control system to measure wheel velocity. The driving roller additionally integrates torque and speed measurement.  
         [0037]     Each road simulator actuator  50  has a carrying capacity of over 50 kg. In the case of a vehicle passenger car or trucks an road simulator actuator can have a carrying capacity of over 1500 KG. In addition to being able to provide greater than +/−50 mm displacement along the X, Y, and Z axis, each actuator is capable of providing angular displacement (RX, RY, and RZ axis) of greater than six degrees. As best seen in  FIG. 22 , a plurality of hydraulic actuators  64  are incorporated into the road simulator actuator  50  are capable of providing acceleration at 35 G&#39;s at frequencies reaching about 25 HZ of the carrying capacity of the road simulator actuator.  
         [0038]     In the case of a vehicle passenger car or trucks an road simulator actuator belt is a 400 mm wide steel or reinforced polymer belt, which is capable of imparting a traction force of up to about 7000 N on a vehicle&#39;s wheel, and is capable of simulating road speeds of up to about 250 KPH. Software incorporated into the controller allows for programming of the tire centerline anywhere along the length of each corner unit, and above the corner unit.  
         [0039]      FIG. 3  depicts the definition of the 6-axis of freedom afforded by the road simulator shown in  FIG. 2 . Each road simulator actuator  50  weighs approximately 250 KG. Provided within each road simulator actuator is a hydraulic (automatic) or manual belt tension adjustment  66 . This system allows for the automatic adjustment of the tension of the belt depending on the varying vehicle parameters such as vehicle weight or speed. Further, it allows for quick belt removal. An associated hydraulic system (not shown), including the accumulator, is incorporated into the base of each road simulator actuator.  
         [0040]      FIGS. 4-6  depict a front and top perspective views of the road simulator actuator according to the teachings of one embodiment of the present invention. The actuator head is generally a trapezoidal or cylindrical structure having top, side, and front and back surfaces. Incorporated into the top surface is the belt. Shown on the front surface are the support structures for the internal drums and bearings which support the belt. Also shown on the front surface is the belt tensioning mechanism. The belt tensioning system  66  incorporates an actuator which applies forces to a bearing supporting the belt. The tension on the belt can be automatically adjusted by the controller utilizing the hydraulic or pneumatic automatic belt tensioner  66 .  
         [0041]      FIGS. 7-9  are rear perspective views of the actuator shown in  FIG. 2 . The road simulator actuator is shown suspended above the base by a suspension arm. The suspension arm functions to hold the actuator above the base while allowing the actuator to float. A number of hydraulic actuators are disposed between the suspension arm and the actuator head. As depicted best in  FIG. 7 , a driveshaft is coupled to a drive frame disposed within the actuator. The drive shaft is additionally coupled to the drive motor through the flexible coupling such as a cv-coupling.  
         [0042]      FIG. 10  is a top view of the actuator. Shown is the continuous loop belt  58 , which functions simulate the road surface as seen by the tires. Additionally, the belt is configured to be able to impose drag onto the tires, should test conditions require. It is envisioned that the belt can be formed of metallic materials such as woven or sheet steel or can be made of synthetic materials. Additionally, the belt can have a three dimensional surface which interacts with the surface of the tire. It is envisioned that this surface can simulate a gravel road or a series of rumble strips.  
         [0043]      FIGS. 11-14  are internal views of the simulator. Shown are two support drums  60  which function to support the belt  58 . Not shown are two optional additional drums  60 ′. The first additional drum functions to support the belt, while the second additional drum is a drive drum. The drive drum is coupled to the flexible coupling  54  through the drive shaft. Additionally shown are the hydraulic actuators  64  which are disposed between the support arm  70  and the road simulator actuator. These hydraulic actuators  64  function to impart the forces onto the vehicle tires by applying forces through the hydrodynamic bearing  62  of the road simulator actuator.  
         [0044]      FIG. 11  depicts an internal view through the front surface of the road simulator actuator. Shown is the automatic belt-tensioner  66  which applies forces to one support drum  60 . The automatic belt-tensioner  66  functions to automatically adjust the tension of the driven belt. The belt-tensioner  66  further is configured to allow the decoupling of the drive belt from the support drums.  
         [0045]      FIGS. 15, 16 , and  22  are depictions of the actuator&#39;s suspension arm  70 . The suspension arm functions to support the road simulator actuator  50  and to act as a conduit for control and feedback signals. Additionally, the hydraulic and pneumatic fluids can be supplied from the hydraulic accumulator in the base of the road simulator actuator.  FIG. 17  is a depiction of a remote control device coupled to the controller.  
         [0046]      FIGS. 28 and 29  disclose perspective front and rear views of a vibration actuator  100  according to a second embodiment of the present invention. The actuator  100  is used with a controller  61  as described above, and is configured to simulate a road for a vehicle by inputting a simulation of a road into a vehicle&#39;s tires. Testing provided by the system can include, but is not limited to, vehicle dynamics, NVH (noise, vibration, and handling), rigidity, natural frequency of vehicle and suspension, etc. Production testing can include end-of-line testing of vehicle driving and/or braking functions.  
         [0047]     The vibration actuator  100  and has an associated water cooled drive motor  102  for quiet operation, which is coupled to a drive shaft by a constant velocity coupling  104 . The constant velocity coupling  104 , allows the motor  102  to be mounted to the base  106  of the system, while an actuator head  108  is suspended on a support member or arm  110 . Each actuator head  108  has a driven belt  112  for either driving or resisting the rotation of the vehicle&#39;s tires. The driven belt  112  is supported by a pair of drums  114  and a bearing  116 , which is optionally a hydrodynamic bearing. The bearing  116  is disposed immediately below the belt wheel interface. Optionally, the bearing  116  may be a high pressure bearing (e.g. from about 25 to 30 bars). The system is configured to measure force in the X, Y and Z-axis on the rolling belt. The driving roller optionally integrates torque and speed measurement.  
         [0048]     As best seen in  FIGS. 29 and 30 , the vibration actuator  100  has six hydraulic actuators  118   a - f.  The actuators  118   a - f  function at the pressures of between about 200 or 300 bars. There are two or three actuators which apply forces to the actuator head  108  in the Z axis ( 118   a - c ), two in Y axis ( 118   d - e ) and one in X axis  118   f . In this regard, forces to the actuator head  108  in the z direction are transmitted through a generally curved actuator arm  120 . The actuator arm  120  is pivotably coupled at a pivot point  122  on the base. Actuator  118   f  is positioned generally parallel to Y axis actuators  118   d  and is configured to apply forces to a first end  124  of the curved actuator arm  120 . This allows for the base to be reinforced on a single side and significantly reduces the complication of the control and fluid line assembly. A second end of the actuator arm  120  (not shown) is coupled to the actuator head  108 . The lengths of lever arms formed by the pivoted actuator arm  120  can be adjusted to displacements and force loads depending on the weight of the head and the type of actuators  118  being used.  
         [0049]     An optional seventh actuator  118   g  is a hydraulic cylinder located between the air bearing  116  and the actuator head  108 . Actuator  118   g  is positioned within a guide to allow only Z-axis displacement. The additional cylinder  118   g  is configured to provide high frequency displacement (vibration simulation from 50 Hz to 150 Hz) with small stroke (about +/−5 mm) directly to the driven belt, and thus the test vehicle tire, without needing to displace the whole actuator head  108 . For vibrations of less than 50 Hz, the main Z-axis actuators  118   a - c  are used. The actuators are coupled to the actuator head  108  by hydrostatic ball-joints which do not create vibration noise at high frequency motion. The relative rotation allowed by these ball-joints is about 20° in any direction.  
         [0050]     The actuators  118   a - f  are generally configured to move an actuator head  108  having a mass of greater than about 250 Kg. Actuators  188   d - f  are configured to apply X &amp; Y axis dynamic forces of greater than 35 kN, while the actuator  118   a - c  are configured to apply dynamic forces of greater than 70 kN. Actuators  118   d - f  are configured to apply X &amp; Y axis displacements of greater than +/−50 mm, while the actuator  118   a - c  are configured to displacements of from about +/−50 mm to +/−150 mm. The actuator  100  provides angular displacements Rx, Ry, and Rz of greater than +/−6 Deg using multiple off axis actuators. Additionally, the actuator provides X &amp; Y axis accelerations of +/−150 m/s 2  and Z axis acceleration of +/−350 m/s 2  and a maximum motion frequency from 50 Hz to 100 Hz.  
         [0051]     As best seen in  FIG. 31 , the actuator head  108  is generally oval shaped and formed on a frame  125  which supports the pair of drums  114  using bearings  126 . The frame additionally supports an automatic belt tensioning mechanism  128  formed of a pair of actuators  134  which can dynamically adjust the tension of the belt. The automatic belt tensioning mechanism  128  adjusts the tension of the driven belt as a function of at least one of belt speed, belt tension or wheel speed. The tensioning mechanism  128  also allows for real time lateral guiding of the driven belt with closed loop control. In this regard, the system is configured to use sensors to determine if the belt is in an incorrect position and uses tensioning mechanism to dynamically adjust the lateral placement of the belt.  
         [0052]     The actuator head  108  additionally as a platen surface  130  that functions to slidably support the rotating belt. The platen surface  130  functions as the dynamic input surface for the whole vehicle road simulator. Disposed within this surface  130  is an aperture  132  which holds the bearing  116  which preferably a porous type bearing surface and a guide for the optional Z-axis actuator  118   g.    
         [0053]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.