Abstract:
A thruster system is provided for a vehicle that can be used to reduce the roll propensity of a motor vehicle. The system utilizes a control system and multiple sets of thrusters which are strategically placed upon the vehicle. The control system is provided for detecting a potential roll condition and activates selected ones of the thrusters to produce a necessary thrust force for counteracting roll forces. The thrusters are connected to an on-board pressurized gas source that generates the anti-roll thrust force.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/562,143, filed on Apr. 14, 2004, the disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an anti-roll system for a vehicle, and more particularly, to an anti-roll system which employs thrusters supplied with on-board pressurized hydrogen or other gas for producing a thrust force for resisting roll forces acting on a vehicle. 
     BACKGROUND OF THE INVENTION 
     Auto manufacturers have developed systems to aid in vehicle stability, such as variable ride height suspension systems, anti-lock braking systems and electronic stability control systems. 
     Auto manufacturers are further developing automobiles having alternative power sources to internal combustion engines. Electrical vehicles having rechargeable batteries and hybrid vehicles using both internal combustion engines and electric motors for driving the vehicle are becoming available. Electrochemical fuel cells are also being developed to serve as an alternate source of electricity for powering electric drive motors of an automobile. An electrochemical fuel cell contains a membrane sandwiched between electrodes. One preferred fuel cell is known as a proton exchange membrane (PEM) fuel cell, in which hydrogen (H 2 ) is used as a fuel source or reducing agent at an anode electrode and oxygen (O 2 ) is provided as the oxidizing agent at a cathode electrode. During operation of the fuel cell, electricity is garnered by electrically conductive elements proximate to the electrodes via the electrical potential generated during the reduction-oxidation reaction occurring within the fuel cell. For on-board vehicle fuel cell systems, the hydrogen can be stored in a pressurized tank that is typically between full fuel (for example, 10,000 p.s.i.) and low fuel (for example, 500 p.s.i.), depending upon the amount the tank is filled and the fuel is consumed. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an anti-roll system that is designed to reduce the roll propensity of a motor vehicle. The system includes a first thruster mounted on a first side of the motor vehicle and a second thruster mounted on a second side of the motor vehicle. Each of the first and second thrusters is provided in selective communication with a source of pressurized gas. The source of pressurized gas can be either pressurized hydrogen which is also utilized in combination with an on-board fuel cell, or a separate pressurized gas source. A controller system is provided for detecting a potential roll condition of the vehicle and releasing pressurized gas from the pressurized gas source to one of the thrusters for generating a counteracting force for resisting the detected potential roll condition. 
     According to one aspect of the present invention, the first and second thrusters are each mounted in a side pillar of the motor vehicle. 
     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 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a front view of a vehicle having a thruster located in the pillars of the vehicle for applying a roll resisting force to the vehicle according to the principles of the present invention; 
         FIG. 2  is a side view schematically illustrating the potential mounting locations of the thrusters and illustrating the pressurized gas piping system according to the principles of the present invention; 
         FIG. 3  is a side view of the vehicle illustrated in  FIG. 2  with the anti-roll thrusters illustrated in an activated state; 
         FIG. 4  is a-flow diagram of a roll-over risk estimation algorithm according to the principles of the present invention; 
         FIG. 5  is a flow diagram of a control algorithm for the anti-roll thruster system according to the principles of the present invention; 
         FIGS. 6   a  and  6   b  are force diagrams illustrating the relevant forces relating to a vehicle during a roll-over condition; 
         FIG. 7  is a graphical illustration of the instantaneous critical roll rate utilized for determining activation of the thrusters according to the principles of the present invention; 
         FIG. 8  is a schematic side view of a second embodiment of the anti-roll thruster system illustrated in a condition where roll-over risk is low; 
         FIG. 9  is a side schematic view of a vehicle shown in  FIG. 8  illustrating the system when the roll-over risk is high; 
         FIG. 10  is a side schematic view of the system shown in  FIG. 8  with the thrusters being activated to apply a resistance force for resisting vehicle roll over according to the principles of the present invention; 
         FIG. 11  is a side schematic view of the system shown in  FIG. 8 , with a nitrogen purging system activated after the roll-over risk has subsided; 
         FIG. 12  is a graphical illustration of the first and second activation thresholds according to the principles of the present invention; 
         FIG. 13  is a flow diagram of a roll-over risk estimation algorithm; 
         FIG. 14  is a flow diagram of an activation algorithm; 
         FIG. 15  is a flow diagram of a reset algorithm according to the principles of the present invention; 
         FIG. 16  is a graph of the thrust force time history of an example thruster system according to the principles of the present invention; and 
         FIG. 17  is a thrust force time history of a stored nitrogen thruster system according to the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     With reference to  FIG. 1 , a vehicle  10  is shown in a potential roll condition relative to a surface  12  with a vehicle  10  having a thruster  14  activated for applying a force (F T ) for resisting the roll forces acting on the vehicle  10 . According to the present invention, the vehicle  10  is provided with one or more thrusters  14  provided on each side of the vehicle and mounted within one of the A pillar, B pillar, or C pillar of the vehicle. It should be understood that the thrusters can be mounted to other advantageous locations of the vehicle, including the engine compartment, trunk, door, or anywhere else where the thruster force is desired and where packaging space can be found with the thrusters. As illustrated in  FIG. 2 , multiple thrusters  14 L can be provided on each side of the vehicle. It should be understood that although thrusters  14 L are illustrated in  FIG. 2  on the left hand side of the vehicle, thrusters (not shown) are mounted to the right-hand side of the vehicle in the same manner as illustrated in  FIG. 2 . 
     The thrusters  14  are connected to a source of pressurized gas such as an on-board pressurized hydrogen tank  16  which also provides hydrogen to an on-board fuel cell system  18  which is utilized for providing electricity for driving electric drive motors of the vehicle. The electric drive motors can be provided at each wheel for providing drive torque thereto as is known in the art. 
     A gas delivery system  20  to each thruster  14 L,  14 R includes a conduit  22  in the form of a pipe or tube having a pressure regulator valve  24  disposed in close proximity to the hydrogen tanks  16  and a fast action valve  26  disposed in close proximity to the thrusters  14 . A controller  30  is provided for controlling the regulator and fast action valves  24 ,  26 . The pressure regulators are used to allow a much lower gas pressure (for example, 500 p.s.i.) than the fuel tank pressure (which can approach 10 thousand p.s.i.) and the piping between the pressure regulator valve  24  and the nozzles  14 . The controller  30  can regulate the pressure regulator valve such that the level of the pressure allowed through the pressure regulator valves can be adjusted based on the severity prediction of a roll event. The passenger side gas delivery system (not shown) is identical to the driver side. 
     A vehicle roll sensor is used by the control module  30  to monitor the instantaneous roll angle and roll rate of the vehicle. A roll risk estimation algorithm is illustrated in  FIG. 4  in which at Step S 1 , the instantaneous roll angle θ and roll rate {dot over (θ)} are monitored. At Step S 2 , the instantaneous roll rate of the vehicle is compared with a predetermined threshold value. If the instantaneous roll rate of the vehicle is not greater than the threshold, as determined at Step S 3 , then the roll over risk is determined to be low, while if the instantaneous roll rate of the vehicle is greater than, or equal to, the threshold value as determined as Step S 4 , the roll-over risk is determined to be high. 
     As illustrated in  FIG. 5 , an anti-roll thruster activation and reset algorithm is shown which is implemented in the control module  30 . Upon determination that the roll risk is high, as illustrated in  FIG. 4 , the algorithm of  FIG. 5  continues to monitor the vehicle roll rate and roll-over risk at Steps S 5  and S 6 . If in Step S 6  it is determined that the roll-over risk is no longer high, instruction is given to close all valves and nozzle doors of the anti-roll system in Step S 7 . If it is determined that the roll-over risk is high at Step S 6 , it is determined whether the roll rate of the vehicle {dot over (θ)} is greater than zero. If it is determined at Step S 8  that the vehicle roll rate {dot over (θ)} is not greater than zero, the algorithm goes to Step S 9  in which the passenger side nozzle doors  32  and fast-action valves  26  are opened. If, at Step S 8  it is determined that the vehicle roll rate {dot over (θ)} is greater than zero, the algorithm proceeds to Step S 10  in which the driver side nozzle doors  32  and valves  26  are opened. 
     As illustrated in  FIG. 3 , the nozzle doors  32  are shown in an open position and a jet of hydrogen gas  48  is expelled from each of the thrusters  14  with the passage  22  being filled with hydrogen since the regulator valve  24  and fast action valves  26  have all been opened. Roll-over risk of the vehicle is estimated by comparing the instantaneous roll angle and roll rate of the vehicle with a predetermined threshold called the “instantaneous critical roll rate” (ICRR), which is established based on roll-over characteristics of the vehicle as determined, for example, from  FIG. 7 . This is determined by setting the threshold value equal to:
 
Threshold= s ×( ICRR )
 
where “s” is a scaling factor which is less than, or equal to, one and greater than zero. The instantaneous critical roll rate is determined from the equation:
 
     
       
         
           
             
               
                 
                   ICRR 
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     As illustrated in  FIGS. 6   a  and  6   b , the value T is the track width, m is the vehicle mass, I CG  is the vehicle&#39;s moment of inertia about the longitudinal axis of the vehicle passing through the gravity center, g is gravity, h CG  is the height of the center of gravity of the vehicle, F TRIP  is the trip force applied to the vehicle that would lead to a potential roll condition, and N is the upward force applied to the vehicle from the ground. 
     For example, an activation threshold of 1.95 radians per second (i.e., 90% of an example vehicle&#39;s critical roll rate value) is chosen as a threshold for the vehicle. If the roll rate of the vehicle as a function of the roll angle exceeds the threshold and, depending on the roll rate, is greater or less than zero, a corresponding set of anti-roll thrusters  14  will be activated to generate thrust forces to resist the roll.  FIG. 3  depicts a side view of the vehicle when the anti-roll thrusters  14  of the driver side are activated. Furthermore,  FIG. 1  depicts a front view of the vehicle with the driver side thrusters activated to counteract any roll forces acting upon the vehicle. 
       FIGS. 8-11  depict another example embodiment of the invention, in which additional fast action valves  38  are added to isolate the piping sections  22  between the nozzle  14  and the fuel tank, and a nitrogen gas purging system including a nitrogen gas tank  40  and purging valves  42  have been added to purge the residue hydrogen in the piping sections  22 .  FIG. 8  shows the state of the anti-roll thruster system when the roll risk is low. The piping sections  22  are illustrated as clear to indicate that there is no hydrogen in the piping sections  22 . Again, only the driver side anti-roll thruster system is illustrated here. The passenger side anti-roll thruster system is identical to the driver side.  FIG. 9  shows the state of the anti-roll thruster system when the roll risk is high. In this condition, the fast action valves  38  have been opened to allow pressurized hydrogen to enter the piping sections  22  which are shaded for purposes of illustrating the hydrogen within the piping sections. Furthermore, the nozzle doors  32  are opened to prepare the anti-roll thruster system and the vehicle for a possible roll event. The nozzle doors  32  can be operated by a servo-motor or by other mechanical and electro-mechanical devices. 
       FIG. 10  shows the state of the anti-roll thruster system when the roll risk is very high (i.e., imminent). In this state, both fast-action valves  38  and  26  are activated and hydrogen jets  48  are shooting from the nozzles of the thrusters  14  to generate an anti-roll thrust force. In  FIG. 10 , the pipe sections  22 , thrusters  14 , and jets are all shaded in order to illustrate the hydrogen gas. 
       FIG. 11  depicts the activation of the nitrogen purging system when the roll risk has subsided. During a nitrogen purging process, the purging valves  42  are opened to allow nitrogen from tank  40  to purge remaining hydrogen from the piping sections  22  and thrusters  14 . After purging the piping system with nitrogen gas, the anti-roll thruster system will be back to the normal state as shown in  FIG. 8 , and the system will be ready to be used again. 
       FIG. 13  illustrates a risk evaluation algorithm utilized by the controller  30 . In the risk assessment algorithm, the control monitors the instantaneous vehicle roll angle (θ) and roll rate ({dot over (θ)}) and compares the absolute value of the instantaneous vehicle roll rate (|{dot over (θ)}|) with a first threshold value at Step S 102 . If the absolute value of the instantaneous roll rate is not greater than the threshold value, the roll-over risk is determined to be low at Step S 103 . If the absolute value of the instantaneous vehicle roll rate (|{dot over (θ)}|) is greater than the first threshold value, then it is determined at Step S 104  if the absolute value of the instantaneous vehicle roll rate (|{dot over (θ)}|) is greater than a second threshold value. If it is determined that the absolute value of the instantaneous vehicle roll rate (|{dot over (θ)}|) is not greater than the second threshold value, then it is determined at Step S 105  that the roll-over risk is high. However, if it is determined at Step S 104  that the absolute value of the instantaneous vehicle roll rate (|{dot over (θ)}|) is greater than a second threshold value, it is determined at Step S 106  that the roll over risk is very high. 
     In  FIG. 14 , an activation algorithm is illustrated which monitors at Step S 107  the vehicle roll rate and roll over risk. At Step S 108 , it is determined whether the roll over risk is high. If it is determined at Step S 108  that the roll over risk is not high, it is determined at Step S 109  whether the roll over risk is very high. If at Step S 109  it is determined that the roll-over risk is not very high, the control proceeds to Step S 110  where it is determined whether the roll-over risk was previously determined to be high or very high at Step S 110 . If not, the control returns to Step S 107  and if so, the control goes to Step S 11  wherein the anti-roll system is reset and the control then returns to Step S 107 . If after Step S 108  it is determined that the roll over risk is high, it is determined at Step S 112  whether {dot over (θ)}&gt;0. If at Step S 112  it is determined that {dot over (θ)}&gt;0, then the driver side nozzle doors  32  and fast acting valves  38  are opened at Step S 114 . If at Step S 112  it is determined that {dot over (θ)} is not greater than zero, then the passenger side nozzle doors  32  and fast acting valves  38  are opened at Step S 115 . If it is determined that the roll-over risk is very high at Step S 109 , then at Step S 116 , it is determined whether the roll rate {dot over (θ)} is greater than zero, and if so, the driver side fast-acting valves  26  are opened at Step S 117 . If at Step S 116  it is determined that the vehicle roll rate {dot over (θ)} is not greater than zero, the passenger side fast-acting valves  26  are opened at Step S 118 . 
       FIG. 15  is a flow diagram of an anti-roll system reset algorithm according to the principles of the present invention. As illustrated in  FIG. 15  at Step S 201 , it is determined whether the valves  38  on the driver side are open. If so, valves  38  are closed at Step S 202 . Next, at Step S 203 , the fast-acting valves  26  are opened and at. Step S 204 , the nitrogen purge valves are opened. The nitrogen purge valves  42  are maintained opened for a predetermined time delay. At Step S 205 , and subsequently, the nitrogen purge valves  42  are then closed at Step S 206  and the fast-acting valves  26  are closed at Step S 207 . At Step S 208 , the driver side thruster doors  32  are then closed and the algorithm ends. The above sequence of Steps S 202 -S 208  provides a sequence of steps for resetting the anti-roll system for the thrusters on the driver side of the vehicle. A similar group of Steps S 302 -S 308  is carried out for resetting the anti-roll system on the passenger side of the vehicle. Since the steps are identical but simply applied to the passenger side valves, a detailed description will be omitted. 
     The present invention utilizes an energy compensation method to minimize the size of the thruster nozzles  14 . Specifically, the nozzles  14  are so designed that they will do anti-roll work equivalent to the difference between the one-quarter turn roll-over kinetic energy of a given hydrogen-powered vehicle and a target value. An acquired mass flow rate and nozzle throat area are then calculated based on the additional work. Using this method, the size of the nozzles can be minimized for ease of packaging. For example, the graph of  FIG. 15  estimates that two nozzles, each with a 35 mm diameter throat, together with a 176 liter fuel tank under a pressure as low as 500 p.s.i. (5% of the assumed 10 thousand p.s.i. fuel tank pressure), would be sufficient to achieve improved roll stability. In this case, the work done by the anti-roll system is approximately 1.6 kJ. 
     The proposed anti-roll thruster system could also be used for non-hydrogen powered vehicles if a large volume and/or high pressure gas source is added to the vehicle such as the nitrogen tank  40  as illustrated in  FIGS. 8-11 .  FIG. 17  graphically illustrates that two nozzles, each with a 35 mm diameter throat, together with a 2.356 liter nitrogen tank under pressure of 7500 p.s.i. would be sufficient for an exemplary non-hydrogen powered vehicle to provide a required thrust energy of 1.61 kJ to counteract significant roll forces. 
     It will be appreciated that the thruster system could also be used for anti-pitch. The anti-roll thruster system could also be used for dumping the hydrogen fuel when a severe crash event is detected by other onboard crash sensors, such as an airbag sensor, to lower the risk of post-crash damage. For example, an airbag deployment signal could be used to open the fast action valves to timely dump the high pressure hydrogen gas in the fuel tank to atmosphere to avoid post-crash hazards. 
     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.