Abstract:
This invention relates to a universal brake system (UBS) that combines features from an adjustable wheel traction system (WTS) and an improved anti-lock brake (ABS) system. The WTS provides a plurality of extendable and retractable spikes contained in a wheel assembly or wheel adapter to increase traction (friction) between a vehicle&#39;s wheel and its supporting surface. To further improve wheel traction each wheel spike has different types of changeable heads for different types of terrain and road surfaces. When operating in dry road mode, the UBS operates as an anti-lock braking system except the spikes can operate during emergency braking to provide additional traction between the tire and wheel support surface. When operating in slippery road mode, the UBS activates the WTS for increase traction control and utilize an improved computer controlled anti-lock braking system to alternate between wheel lock and anti-lock brake with skid control to provide the ultimate solution to decreasing a vehicle&#39;s stopping distance and controlling a vehicle&#39;s skid on slippery and dry road surfaces.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS (MPEP 201.11) 
       [0001]    61/881,916 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT: (MPEP 310) 
       [0002]    None 
       THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT (37 CFR 1.71 (g) 
       [0003]    None 
       REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON COMPACT DISC AND AN INCORPORATION-BY-REFERENCE OF THE MATERIAL ON THE COMPACT DISC 
       [0004]    None 
       BACKGROUND OF THE INVENTION ((MPEP 608.01(c)) 
       [0005]    European Patent 1 603 781 B1 and U.S. Pat. No. 5,479,567A discloses an anti-skid control apparatus for a braking system of a vehicle having a left and right front wheels and left and right rear wheels. There are no federally sponsored research or development involved with this invention. These braking system are considered as prior art. This disclosed braking system includes: an adjustable modulator (not shown), for increasing a hydraulic pressure to oil cylinders of the left and right, and front and rear wheels of the vehicle in a hydraulic pressure increase mode, holding as is the current value of the hydraulic brake pressure in a hydraulic pressure holding mode, and for reducing the hydraulic brake pressure to the oil cylinder of said left and right, and said front and rear wheels of said vehicle in a hydraulic pressure reduction mode; a detection means for detecting the speed of said left and right, and said front and rear wheels of said vehicle; a slip detection means for judging by evaluating signal outputs from said detection means whether or not a slip of the extent to which anti-skid control is necessary has been generated in any of the front, rear, left and right wheels of said vehicle and a controller which controls the modulator based on the judged result of said slip detection means, and which selects and sets one of said hydraulic pressure increase mode, said hydraulic pressure holding mode and said hydraulic pressure reduction mode for each wheel. The controller provides an anti-skid control setting means for setting an anti-skid control for the wheel; the slip detection means judged that the anti-skid control is necessary; a hydraulic pressure control means for setting said adjustable modulator at either the pressure maintaining mode or the pressure reduction mode with regard to the wheel for which the anti-skid control has been set by said anti-skid control setting means until the slipping which triggered the anti-skid control disappears, and, when the slipping disappears, for setting the adjustable modulator at the pressure increase mode in condition that the wheel speed of the wheel is increasing; and a pressure increase restriction means for determining whether slip is increasing at the pair of front or rear wheels to which the wheel the pressure increase mode is set does not belong, and converting the pressure increase mode to either the pressure maintaining mode or the pressure decrease mode if the slip at the pair of front or rear wheels is increasing. 
         [0006]    An Anti-lock Brake System (ABS) is often included as standard equipment on new vehicles. However, an ABS alone has proven to be ineffective with controlling a vehicle&#39;s skidding on slippery rigid surfaces such as wet roads, ice or snow covered roads and non-ridge surfaces such as sand and loose gravel. The obvious problem is that standard rubber tires or even specialize tires with customize treads offer very little traction on the above mention road surfaces especially during heavy braking conditions which in most cases lead to an out of control skidding vehicle. This situation can only be remedied with the intervention of a device that can re-establish traction (friction) between a wheel and its supporting surface and then applying a combination of anti-lock brake with skid control and locking brake when the demand for a rapid stop on slippery road surfaces is required. Hence the invention provides a solution to the problem by providing an adjustable wheel traction system integrated with prior-art ABS technology. The new integrated braking system invention is called a universal braking system (UBS). 
       BRIEF SUMMARY OF INVENTION 
       [0007]    1) This invention relates to a universal brake system (UBS) that combines features from a prior art anti-lock brake system (ABS) with a new technology called an adjustable wheel traction system. This combination of technology provides a vehicle operator with the ability to control skidding and reduce a vehicle stopping distance on dry surfaces and particularly on slippery road surfaces e.g. wet roads, ice covered roads, snow covered roads and non-rigid surfaces such as sand and loose gravel. It is important to note that today&#39;s conventional ABS&#39;s are most effective on dry rigid road surfaces e.g. concrete or asphalt and less effective on slippery wet roads, icy or snow covered rigid road surfaces and non-rigid surfaces such as sand and loose gravel. This is due to the obvious lack of tire traction on these types of road surfaces which can make controlling a vehicle&#39;s skidding almost impossible with just an ABS. Hence, the invention of the UBS solves the problem with the lack of wheel traction (friction) and skid control on dry, wet, frozen and slippery roads by utilizing an adjustable wheel traction system that can extend and retract wheel spikes on demand as a result of a vehicle operator pressing a vehicle&#39;s brake pedal, and using the brake controller systems to alternate between locking a wheel on a spike long enough time for it to penetrate one of said mentioned types of road surfaces and then measuring the wheel slip of the rear wheel and switching back to anti-lock and anti-skid mode momentarily. This cycle is repeated until the slip that cause the wheel to lockup goes away. 
         [0008]    2) The wheel traction system consist of a plurality of spikes embedded in a wheel&#39;s housing and controlled by a brake system microprocessor controller which can automatically upon an operator pressing a vehicle&#39;s brake pedal extend spike rod  14  outward beyond a wheel&#39;s supporting surface in order to create friction (traction) with a wheel&#39;s supporting surface. Spikes are automatically retracted when a vehicle&#39;s operator release the brake pedal if the unit is operating in the automatic mode. 
         [0009]    3) The wheel traction system has several modes of operation that determines how much the plurality of spikes extends outward beyond a wheel surface. The modes of operation are based on the types of road surfaces and road conditions a vehicle will is driven on. Here is a summary of the different modes of operation: A) Dry mode—no spikes are extended except under emergency braking conditions otherwise the braking system works as an anti-locking braking system with continuous wheel slip control. B) Wet Mode—A plurality of spike are extended a predetermined distance upon a vehicle operator pressing a vehicle brake pedal. In this mode, the braking system microprocessor controller allows a wheel to momentary lockup on a spike long enough time for it to dig-into the vehicle supporting surface in order to create traction (friction) between a tire and its supporting surface. C) Ice Mode—works the same as wet mode except the predetermined distance that spikes are extended is a little more than in the wet mode. D) Snow Mode—works the same as the ice mode except the predetermined distance spikes are extended is a little more than the ice mode. 
         [0010]    4) The wheel traction system has two configurations: a) The wheel traction system is integrated into a vehicle&#39;s wheel assembly  FIG. 5 . This configuration is best suited for new vehicles or vehicles that are having their wheels replaced in order to take advantage of the safety features of the wheel traction system. b) The second configuration is an independent adapter to be mounted outside of an existing vehicle&#39;s wheel. This configuration is designed mainly to adapt to an existing vehicle wheel. 
         [0011]    5) Power for the wheel traction system is via a fly wheel generator mounted inside a wheel assembly or adapter assembly, a battery pack and a solar panel with charge controller. The unit can also be powered optionally from a vehicle&#39;s power system via hardwiring not shown. 
         [0012]    6) Communication to the wheel retraction system is via a wireless remote terminal unit (RTU)  33  microprocessor controller mounted internally to the wheel assembly or adapter assembly and communicates wirelessly with a vehicle&#39;s wireless brake RTU  50  controller and/or engine control unit (ECU). An alternate method of communication is via hardwired connections between RTU&#39;s and ECU. 
         [0013]    7) A plurality of spikes are mounted on a circle disc with each spike having its own gear  16  that mesh with a gear on the gear disc  23 . Each spike has a solenoid  25  control latch  26  that allows the spike to be release and extend under the power of a stepper motor  21  and latch in place when extended. Each spike has means to absorb shock via spring  14 A. Solenoid  25  pulls the latch  26  away from spike teeth to allow the spike to retract under the power of spring  17  when a brake pedal is released. Individual wheel rotational velocities are controlled by selective operation of dump and apply valves that control the wheel brake pressure applied at each of the wheels. The operation of the valves provides three modes of operation, namely, dump to reduce the applied pressure, apply to increase the applied pressure, and hold to maintain the applied pressure at the current level. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1 . Wheel Traction System Adapter Assembly—Shows the components and assembly of a wheel traction system adapter attached to a vehicle&#39;s wheel. 
           [0015]      FIG. 2 . Wheel Traction Adapter Assembly Left Side view—A side view of the assembly of a wheel traction system attached to a vehicle&#39;s wheel. 
           [0016]      FIG. 3 . Wheel Traction Assembly with Spikes Retracted Front View—A front view of the wheel traction system with the spikes retracted. 
           [0017]      FIG. 4 . Wheel Traction Assembly with Spikes Extended Front view—A front view of the wheel traction system with the spikes extended. 
           [0018]      FIG. 5  Wheel Traction System Installed Inside Wheel Assembly—illustrates how the wheel traction system is installed inside a vehicle&#39;s wheel. 
           [0019]      FIG. 6 . Wheel Traction System Major Component Wiring Diagram—Illustrates the wiring of major components of the wheel traction system. 
           [0020]      FIG. 7 . Universal Braking System Schematic—Shows how electrical components of the UBS are wired and there location in a vehicle. 
           [0021]      FIG. 8 . Wheel Traction System Adapter Schematic block diagram—Illustrates the wiring of major computer components of the wheel traction system. 
           [0022]      FIG. 9 . Wheel Position Sensor Assembly—illustrates how start and stop detectors and magnetic sensors are installed on a vehicle&#39;s wheel. 
           [0023]      FIG. 10 . Universal Braking System overall system components—A schematic diagram showing major components of the UBS installed in a rear wheel vehicle. 
           [0024]      FIG. 11 . Universal Braking System Computer Algorithm—A flow chart of the braking system computer algorithm that is in accordance with the invention 
           [0025]      FIG. 11A . Universal Braking System Computer Algorithm—Continuation from  FIG. 11 . 
           [0026]      FIG. 12  ABS Prior Art References—Vehicle speed sensor signal circuit combination and a typical vehicle brake and wheel assembly with ABS components installed. 
           [0027]      FIG. 13 . Magnetic Position Detector—Assembly drawing of the wheel position sensors and detectors. 
           [0028]      FIG. 14  illustrates the pressure being applied to one of the wheel brake cylinders as a function of time. At t 1  the brake pedal  12  is depressed to begin applying pressure to the brake cylinders. 
           [0029]      FIG. 15  shows the actual vehicle speed during heavy braking application in the slippery road mode with wheel traction system active. The actual wheel speed begins to decrease relative to the actual vehicle speed as heavy braking begins. Mean while, the microprocessor in the ECU  54  has calculated a theoretical speed ramp based on the selected slippery road surface that represents the speed the vehicle would travel when decelerated at a predetermined maximum rate, such as 1.0 g. When the difference between the actual wheel speed and the calculated speed ramp exceeds a predetermined slip threshold S t , it is an indication that the wheel has potential to lock-up at t 1 . The ECU then reads the spike the start detector  44  on the slipping wheel for the next available spike, reads the spike status switch  42  for an OK on the spike extension, then the microprocessor causes the apply valve associated with the wheel brake to close, as illustrated in  FIG. 19 , causing the wheel to lockup for a predetermined amount of time up to t 2 . The wheel speed remains at zero until t 2  at which time the ECU selectively reduce the pressure of the hydraulic fluid being applied to the wheel cylinder. Accordingly, the ECU microprocessor applies a series of pulses labeled shown in  FIG. 18  to the dump valve associated with the wheel cylinder to lower pressure sufficiently to cause the wheel to spin back up until the slip threshold is reached again then repeat the lock wheel cycle over until the vehicle has come to a stop or the vehicle operator has reduced brake pedal pressure below a set pressure threshold. Once a wheel has locked, the wheel spikes will remain extended for a predetermined time to prevent the vehicle from immediately re-entering a skid on a slippery surface. 
           [0030]      FIG. 16  shows the actual vehicle speed during the brake application in the dry road mode as a function of time is illustrated by the line labeled  92 . After t 1 , the actual wheel speed  93  begins to decrease relative to the actual vehicle speed  92 . Mean while when the microprocessor detects that the wheel deceleration has reached a predetermined threshold value, such as 1.3 g, at t 2 . The microprocessor continues to monitor the speed of the wheel relative to both the actual wheel speed and theoretical speed ramp. When the microprocessor detects that the wheel deceleration has reached a predetermined threshold value, such as 1.3 g, at t 2 , the microprocessor causes the isolation valve associated with the wheel brake to close, as illustrated in  FIG. 17 , limiting the pressure applied to the wheel cylinder of a constant level P A  in  FIG. 14 . 
           [0031]      FIG. 17  shows at t 2  the microprocessor in dry road mode causes the isolation valve associated with the wheel brake to close, and limiting the pressure applied to the wheel cylinder of a constant level P A . The uncontrolled wheel brake pressure would continue to follow the dashed curve labeled  45  in  FIG. 2A . 
           [0032]      FIG. 18  illustrates the operation of the dump valve in the dry road mod. Upon correction of the second wheel speed departure with a second series of dump pulses, it is seen that the applied pressure P C  while lower that the initial pressure P A , as shown in  FIG. 14  is greater than the pressure P B  present after correction of the first wheel speed departure. Thus it is seen that the UBS provides control over the individual wheel speeds by switching between hold, dump and apply modes of operation of the solenoid valves included in the control valve  16 . 
           [0033]      FIG. 19  Illustrates the operation of the apply valve for dry road mode. It is desirable for the ECU microprocessor to apply a series of pulses at t 5  to the apply valve associated with the wheel cylinder to raise the pressure . . . These pulsed precipitate a second wheel speed departure at t 6 . 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0034]    The universal braking system disclosed comprises: 
         [0035]    An adjustable wheel traction system configured as either a standalone wheel adapter or integrated into a vehicle&#39;s wheel assembly comprising: 
         [0036]    An adapter housing  24   FIG. 1  containing a plurality of spikes  14  with teeth for latching to solenoid  25  and mounted internally to housing in a circular pattern and capable of automatically extending under the power of a stepper motor  21  and retracting under the power of spring  17 , means for spike to absorb shock via spring  14 A, said spike has interchangeable terrain adapters  27  and  27 A used to improve friction between a tire a wheel&#39;s supporting surface, said spike has sleeves  15  to protect spike from debris and other foreign matter, outer rim of adapter housing  24  is a flexible surface  10  capable of supporting a vehicle if the main tire becomes flat, said housing contain plurality of elongated water tight cavities  42 B running parallel to each spike and combining in a circular ring and containing an antifreeze coolant with an electric heating element  42 A for heating said fluid, each said spike  14  contains a gear  16  that mesh with a mating gear  19  mounted near outer edge of main gear disc  23 , said mating gears  19  are mounted in a slot and under spring tension to allow said gear to move under spike gear  16  if a spike becomes stuck, said gears diameter is set to determine the maximum distance each spike can extend, said spikes extend outward pass a tire supporting surface a predetermined distance in order to cause friction (traction) with a tire&#39;s supporting surface, said spike is extended a predetermined distance selected based on the friction coefficient of a tire&#39;s supporting surface such as that of slippery wet road, ice covered road, snow covered road, sand covered road or loose gravel road, said spike extend and retract proportionate to the amount of brake pedal  67  pressure being measure by brake pedal pressure sensor  68 , said spikes contain means for locking extended spikes with latching solenoid  25  and ratchet lever  26 , said spike is mechanically in contact with normally closed micro switch  42  that opens when a spike has extended outward from its housing, a means for self powering unit via a fly wheel generator  32  centrally mounted, said fly wheel  30  of generator builds up angular momentum as a vehicle&#39;s wheel rotates, said fly wheel rotates during braking to cause generator shaft to turn generator and produce electricity to power unit, said fly wheel generator  32  also provides power to charge a battery  35  via a charge controller  36  that is centrally mounted, a solar panel is mounted on the outside wall of adapter cover housing  29  and provides electricity when there is sun light to charge battery  35  via a charge controller  36 , all electrical component are controlled by a centrally mounted wireless remote terminal unit RTU controller  33  mounted inside adapter housing or inside wheel assembly and is capable of wireless communication with the brake system wireless RTU controller  52  and engine control unit (ECU)  54  per computer algorithm in  FIG. 11 , said RTU  50  has a display  46  to display the status of system components, as an alternate configuration, wheel traction system can be part of a vehicle&#39;s wheel assembly  FIG. 5  with all the features mention above, in addition both configurations can be configured for wireless communication with the braking system computer  FIG. 7  and operate per computer algorithm  FIG. 11 . To provide complete wheel traction and skid control on dry, wet, frozen, slippery, rigid and non rigid road surfaces, the UBS integrates the above mention wheel traction system with features from prior art European Patent 1 603 781 B1 Anti-Lock Braking System. This combination makes the UBS a multifunctional system that is capable providing a vehicle with additional wheel traction and skid control on dry, wet, frozen, slippery, rigid and non rigid road surfaces depending on the terrain adapter selected and the depth of penetration of the wheel spikes. Configured as a standalone wheel adapter  FIG. 1  the wheel traction system per computer schematic  FIG. 8  can be controlled by a vehicle operator with wireless communications from its main remote terminal controller (RTU)  33  to a second wireless RTU  50  mounted inside of a vehicle with operator inputs from a rotary switch  49  for operator to select a predetermined amount of spike penetration distance based on a tire&#39;s supporting surfaces e.g. wet road, ice covered road or snow covered roads and inputs from rotary switch  48  that selects manual traction or automatic traction. A fully configured UBS has the following modes of operation: 
       Traction Modes 
       [0000]    
       
         
           
             Manual Traction—Function as an adjustable wheel traction system with spikes locked in a fully extended position. Spikes extended length is selectable based on road conditions e.g. wet conditions, Icy conditions, snowy conditions. 
             Auto Traction—Function as an adjustable wheel traction system with spikes extending automatically and proportionate to the amount of brake pedal pressure. Spikes extension length is selectable based on road conditions e.g. wet conditions, icy conditions, or snowy conditions. 
             Slippery Roads—Functions as a complete universal brake system that alternate between lock brakes and anti-lock brakes controls while using an adjustable wheel traction system to gain traction on slippery rigid and non rigid road surfaces such as wet roads, ice or snow covered roads or non-rigid surfaces such as sand or loose gravel covered road surfaces. Spikes extended length is selectable based on road conditions e.g. wet conditions, icy conditions, and snowy conditions. 
             Dry Road—Function as an anti-lock brake system with continuous slip control. Wheel traction system is inactive in this mode. 
             For all modes the terrain adapter  27  and  27 A are selected to match road conditions in order to create the maximum amount of friction between a tire or wheel supporting surface. 
           
         
       
     
         [0042]    In manual spike mode said spikes stay extended a fix predetermined distance based on road conditions. In this mode said spikes  14  will stay extended until the unit is switch to automated mode or any other position, In automatic spike mode spikes will extend and retract proportionate to the brake pedal  67   FIG. 10  with pressure measured by sensor  68 . Spikes extension length is selectable based on road conditions e.g. wet condition, icy conditions, and snowy conditions. In slippery mode the system is characterized as having all the features of a universal brake system. The wheel traction system described above is active upon an operator pressing said brake pedal  67  a long with brake switch  67 A closing will cause a brake pressure to be measured at sensor  68 , said spikes will extend proportionately to the amount of brake pedal pressure based on road conditions, e.g. wet conditions, icy conditions, or snowy conditions, a means for measuring wheel speeds ( 77 , 78 , 79 , 80 )  FIG. 10 , a means to detect the start position  44  and stop position  43  of each spike, a means for sensing  42  when a spike has extended from its housing, a means for extending spikes from their housing via stepper motor  21  and gear disc  23  and retracting said spikes via power from spring  17 , a wireless communication means for interfacing with brake system computer  52  and ECU  54 , a road condition switch  49  to select a predetermined depth of penetration of spikes based on the friction coefficient of different type of road surfaces and other conditions previously mentioned above, a fly wheel generator  32  centrally mounted in a wheel assembly  FIG. 5  or in adapter assembly  FIG. 1  for supplying power to all system components, a solar panel  40  and charge controller  36  and a battery pack  35  with entire unit constructed in a matter that keeps a wheel mechanically balanced; there is an adjustable modulator (not shown), for increasing a hydraulic pressure to oil cylinders of the left and right, and front and rear wheels of the vehicle in a hydraulic pressure increase mode, holding as is the current value of the hydraulic brake pressure in a hydraulic pressure holding mode, and for reducing the hydraulic brake pressure to the oil cylinder of said left and right, and said front and rear wheels of said vehicle in a hydraulic pressure reduction mode; a detection means for detecting the speed ( 77 A, &amp; 78 A) of said left and right, and said front and rear wheels ( 70 A,  80 A) of said vehicle; a slip detection means for judging by evaluating signal outputs from said detection means whether or not a slip of the extent to which momentary wheel-lock control is necessary to allow spikes time to penetrate slippery surface in order to generate traction (friction) between a tire on the wheel and supporting tire surface in any of the front, rear, left and right wheels of said vehicle and a controller  52  which controls the modulator based on the judged result of said slip detection means, and which selects and sets one of said hydraulic pressure increase mode, said hydraulic pressure holding mode and said hydraulic pressure reduction mode for each wheel. The braking controller provides the ability to read the spike start detector  44  to detect the next available spike, read the spike status switch  42 , and then lock-wheel for a predetermined time on next available spike once it passes under the stop detector  43 , each momentary wheel-lock to be followed by a return to the anti-lock mode with anti-skid control, after each initial wheel-lock condition spikes will remain extended for a predetermined time to insure vehicle does not immediately return into a skid; when in slippery mode the slip detection means judged that the locked brake control is necessary based on a predetermined slip threshold setting; a hydraulic pressure control means for setting said adjustable modulator at either the pressure maintaining mode or the pressure reduction mode with regard to the wheel for which the momentary locked brake control has been set by mode control switch  49  which sets the brake lock control setting and then alternating back and forth between locked brake mode and anti-lock brake mode until the slipping which triggered the lock brake control disappears  FIG. 16 , when the slipping disappears, set the adjustable modulator to the pressure increase mode such that the wheel speed of the wheel is increasing; and a pressure increase restriction means for determining whether slip is increasing at the pair of front or rear wheels to which wheel the pressure increase mode is set does not belong, and converting the pressure increase mode to either the pressure maintaining mode or the pressure decrease mode if the slip at the pair of front or rear wheels is increasing. In the event the spikes fail to extend as measured by UBS controller reading a closed switch for all spikes status switches  42  after UBS controller command to extend spikes, next UBS controller will energize latching solenoids to release wheel spikes and then momentarily enters dump mode to relieve brake pressure and allow wheel to spin up such that the spikes can be released by centrifugal force, after detection of an opened spike status switch  42  UBS controller releases solenoid to latch spikes in place. UBS brake controller to operate per computer algorithm in  FIG. 11 . 
         [0043]    Dry Surface Mode—which includes an adjustable modulator (not shown), for increasing a hydraulic pressure to oil cylinders of the left and right, and front and rear wheels of the vehicle in a hydraulic pressure increase mode, holding as is the current value of the hydraulic brake pressure in a hydraulic pressure holding mode, and for reducing the hydraulic brake pressure to the oil cylinder of said left and right, and said front and rear wheels of said vehicle in a hydraulic pressure reduction mode; a detection means for detecting the speed of said left and right, and said front and rear wheels of said vehicle; a slip detection means for judging by evaluating signal outputs from said detection means whether or not a slip of the extent to which anti-skid control is necessary has been generated in any of the front, rear, left and right wheels of said vehicle and a UBS controller which controls the modulator based on the judged result of said slip detection means, and which selects and sets one of said hydraulic pressure increase mode, said hydraulic pressure holding mode and said hydraulic pressure reduction mode for each wheel. The UBS controller provides an anti-skid control setting means for setting an anti-skid control for the wheel; the slip detection means judged that the anti-skid control is necessary; a hydraulic pressure control means for setting said adjustable modulator at either the pressure maintaining mode or the pressure reduction mode with regard to the wheel for which the anti-skid control has been set by said anti-skid control setting means until the slipping which triggered the anti-skid control disappears, and, when the slipping disappears, for setting the adjustable modulator at the pressure increase mode such that the wheel speed of the wheel is increasing; and a pressure increase restriction means for determining whether slip is increasing at the pair of front or rear wheels to which the wheel the pressure increase mode is set does not belong, and converting the pressure increase mode to either the pressure maintaining mode or the pressure decrease mode if the slip at the pair of front or rear wheels is increasing. 
         [0044]    Referring to the drawings, illustrated in  FIG. 10  is a typical hydraulic brake system which includes prior art anti-lock brake system (U.S. Pat. No. 5,479,567A) integrated with invention Wheel Traction System. The brake system in  FIG. 10  shown is for a rear wheel drive vehicle. The universal braking system includes a brake pedal  67  that is mechanically connected to a brake light switch  67 A and a dual reservoir master cylinder  69 . A first reservoir of the master brake cylinder  69  provides hydraulic brake fluid to a front wheel brake circuit, while a second reservoir supplies hydraulic fluid to rear wheel brake circuit. 
         [0045]    The master cylinder first reservoir is connected to an UBS control valve  70  by a first hydraulic line  75  the second reservoir is connected to the control valve  70  by a second hydraulic line  76 . The UBS control valve  70  includes a plurality of normally open and normally closed solenoid valves (not shown) and a separate source of pressurized hydraulic fluid, such as a motor driven pump (not shown). The pump is typically included in the body of the control valve  70  while the pump is mounted upon the exterior thereof. The control valve  70  is connected by first pair lines  72  and  71  to right and left front wheels  78  and  77 , respectively. For the vehicle in  FIG. 10 , the front wheels  78  and  77  are non-driven also having front wheel and/or all wheel drive. Similarly, second pair of hydraulic brake lines  74  and  73  connects  70  to right and left rear vehicle wheels respectively. 
         [0046]    Typically, the control valve  70  includes a normally open solenoid valve (not shown) between each of the brake circuits and the corresponding master cylinder reservoir. Upon actuation, the valve closes to isolate the brake circuit from the master cylinder  69 . Accordingly, the valve is typically referred to as an isolation valve. For optimal control of the speed of each of the vehicle wheels, each of the wheel brakes can be provided an associated isolation valve. The control valve also typically includes a first normally closed valve (not shown) for each wheel brake that connects the wheel brake cylinder with a brake fluid reservoir (not shown). Upon actuation, the first normally closed valve is opened to bleed hydraulic fluid from the wheel brake cylinder and thereby reduce the pressure applied to the wheel brake. Accordingly, the first normally closed valve is usually referred to as a dump valve. The control valve also usually includes a second normally closed valve (not shown) for each wheel brake that connects the wheel brake cylinder with an outlet of the pump. Upon actuation, the first normally closed valve is opened to supply pressurized hydraulic fluid from the pump to the wheel brake cylinder and thereby raise the pressure applied to the wheel brake. Accordingly the second normally closed valve is usually referred to as an apply valve. The reservoir connected to the dump valves is connect to the pump inlet and thereby supplies hydraulic brake fluid to the motor driven pump. 
         [0047]    The speed of the front wheels  78  and  77  are monitored by a first pair of wheel associated wheel speed sensors  78   a  and  77   a,  respectively. Similarly, the speed of wheels  80  and  79  of associated wheel speed sensors  80   a  and  79   a,  respectively. 
         [0048]    The wheel speed sensors  77   a,    78   a,    79   a  and  80   a  are electrically connected to an UBS electronic control unit ( 54 ). Closing the brake switch  67   a  provides a signal to the ECU  54  that the vehicle brakes have activated. The ECU  54  also is electrically connected to the pump motor and the actuation coils of the solenoid valves included with the control valve  70 . The ECU  54  includes a microprocessor with a memory that stores a program that that run per the UBS control algorithm  FIG. 11 . 
         [0049]    During vehicle operation in the dry mode/anti-lock mode, the microprocessor in the ECU  54  continuously receives speed signals from the wheel speed sensors  77   a,    78   a,    79   a  and  80   a  and from the spike position detectors ( 43  &amp;  44 ) for each wheel via wireless remote terminal unit  45 . The operation of the UBS operating in the dry mode/anti-lock brake with anti-skid is illustrated by the waveforms shown in  FIG. 14 ,  FIG. 16 ,  FIG. 17 ,  FIG. 18 , &amp;  FIG. 19 . A line labeled  90  in  FIG. 14  illustrates the pressure being applied to one of the wheel brake cylinders as a function of time. At t 1 , the brake pedal  67   FIG. 10  is depressed to begin applying pressure to the brake cylinders. The actual vehicle speed during the brake application as a function of time is illustrated by the line labeled  92  in  FIG. 16 . After t 2 , the actual wheel speed  93  in  FIG. 16  begins to decrease relative to the actual vehicle speed  92  in  FIG. 16 . Meanwhile, the microprocessor in the ECU  54  has calculated a theoretical speed ramp, shown by the dashed line labeled in  FIG. 15  that represents the speed the vehicle would travel decelerated at a predetermined maximum rate, such as 1.0 g. The microprocessor continues to monitor the speed of the wheel relative to both the actual wheel speed and theoretical speed ramp. When the microprocessor detects that the wheel deceleration has reached a predetermined threshold value, such as 1.3 g, at t 2 , the microprocessor causes the isolation valve associated with the wheel brake to close, as illustrated in  FIG. 17 , limiting the pressure applied to the wheel cylinder of a constant level P A  in  FIG. 14 . The uncontrolled wheel brake pressure would continue to follow the dashed curve labeled  95  in  FIG. 14 . 
         [0050]    When the difference between the actual wheel speed  93  in  FIG. 16  and the calculated speed ramp  94  in  FIG. 16  exceeds a predetermined slip threshold S t , it is an indication that a predetermined slippage is occurring between the actual wheel speed and the vehicle speed and that the wheel has potential to lock-up. This point is shown at t 3  in  FIG. 16 . At this time, the wheel speed has fallen sufficiently that it is desirable to selectively reduce the pressure of the hydraulic fluid being applied to the wheel cylinder. Accordingly, the ECU microprocessor applies a series of pulses labeled shown in  FIG. 18  to the dump valve associated with the wheel cylinder to lower pressure sufficiently to cause the wheel to spin back up to the vehicle speed, beginning at t 4 . The lowered pressure is labeled P B  in  FIG. 14 . 
         [0051]    After the wheel speed attains the vehicle speed, it is desirable for the ECU microprocessor to apply a series of pulses at t 5  to the apply valve associated with the wheel cylinder to raise the pressure. The operation of the apply valve is illustrated in  FIG. 19 . These pulsed precipitate a second wheel speed departure at t 6 . Upon correction of the second wheel speed departure with a second series of dump pulses, it is seen that the applied pressure P C , while lower than the initial pressure P A  is greater than the pressure P B  present after correction of the first wheel speed departure. Thus, it is seen that the UBS provides control over the individual wheel speeds by switching between hold, dump of the solenoid valves included in the control valve  70  when operating in the dry mode. 
         [0052]    Because the speed of each wheel is monitored separately, by utilizing a different algorithm for the microprocessor in the ECU  54 , the system illustrated also may function as a Traction Control System (TCS) and/or a Vehicle Stability Control (VCS) system for dry, wet, ice and snow conditions and for slippery rigid surfaces and non-rigid surfaces when integrated with the wheel traction system.