 for purposes of determining whether the wheelchair is off course and subsequent measures to be implemented. Veer, for example, may occur when driving along a slope. Rear-wheel driven wheelchairs have a tendency of veering downwards instead of, for example, maintaining a straight path perpendicular to the slope. Front-wheel driven wheelchairs tend to veer upwards with respect to the slope. More generally, veering may occur when an external force acts on the wheelchair and thus changes the route the user has indicated via an input device. For example, wind blowing in a cross direction to a wheelchair's driving direction may also cause veering.
In U.S. Pat. No. 6,202,773 and U.S. Pat. No. 6,615,937, which are hereby incorporated by reference in their entirety, a rate-of-turn sensor (such as a gyroscope, an angular rate sensor (e.g., piezoelectric ceramic gyro, model no. CG-16D by TOKIN America), or a combination of accelerometers) is provided to sense or determine an actual turn rate of the wheelchair. The controller for the wheelchair may detect veering by assessing the difference between, for example, a turn rate command and the actual turn rate. Accordingly, inputs from the user's command input device and from the rate-of-turn sensor are compared in order to determine if the wheelchair's actual course is different from the desired course. In case of a difference, the wheelchair's speed may be limited and/or the turn rate may be limited or corrected. U.S. Pat. No. 6,615,937 illustrates a system that includes a second rate-of-turn sensor to detect failure of the first rate-of-turn sensor by comparing the outputs of each rate-of-turn sensor to one another. A failure of the first rate-of-turn sensor can be determined by a change in this comparison.
In U.S. Pat. No. 6,202,773 and U.S. Pat. No. 6,615,937 it is noted that an offset voltage associated with the rate-of-turn sensor may vary with temperature. These patents teach a controller that can determine the offset voltage to correct for temperature offset in the rate-of-turn sensor when the wheelchair is at rest. Temperature changes occurring while the wheelchair is being driven may cause an offset voltage error that may be corrected by the controller the next time the wheelchair is at rest. 1
for purposes of determining whether the wheelchair is off course and subsequent bill to be follow through. Veer, for example, may occur when driving along a gradient. Rear - wheel driven wheelchair give birth a tendency of veering downwards instead of, for example, sustain a straight path perpendicular to the slope. Front - wheel driven wheelchair tend to veer upwards with respect to the slope. More broadly, veering may occur when an external force out acts on the wheelchair and therefore changes the road the user has indicated via an input device. For case, wind blowing in a cross direction to a wheelchair's driving direction may also cause veering. 
 In U.S. Pat. No. 6,202,773 and U.S. Pat. No. 6,615,937, which are hereby incorporated by reference in their entirety, a rate - of - turn sensor (such as a gyroscope, an angular rate detector (for example, piezoelectric ceramic gyro, model no. CG-16D by TOKIN America), or a combination of accelerometer) is provide to sense or determine an actual turn rate of the wheelchair. The controller for the wheelchair may detect veering by assessing the remainder between, for example, a turn rate command and the actual turn rate. consequently, inputs from the user's command input device and from the rate - of - turn sensor are compare in order to determine if the wheelchair's actual course is different from the desired path. In case of a difference, the wheelchair's speed may be specify and/or the turn rate may be limited or corrected. U.S. Pat. nobelium. 6,615,937 illustrates a system that includes a second rate - of - turn detector to detect failure of the first rate - of - turn detector by comparing the outputs of each pace - of - turn sensor to one another. A failure of the first rate - of - bend sensor can be determine by a change in this comparison. 
 In U.S. Pat. No. 6,202,773 and U.S. Pat. No. 6,615,937 it is noted that an offset voltage associate with the rate - of - turn detector may vary with temperature. These patents teach a controller that can determine the offset voltage to correct for temperature offset in the pace - of - turn sensor when the wheelchair is at rest. Temperature changes occurring while the wheelchair is being driven may cause an offset voltage mistake that may be discipline by the controller the next time the wheelchair is at rest. 1
 fog purposes of determininn whether the whgeochair is ofr course and subsequent measures to ue inplemtuted. Veer, for exampld, may occlr when deiviig along a slope. Rear-whecj drjyen wkexlchairs have a tendency mf veering dowtwxrbs instead of, for example, maintainind a strsihht path perpegdicllwr tk the slope. Front-wheel driven wheemchairs tend to veer upwards with respect to tje spope. More generallj, veering mqy osxur when an dxternal force acts on the wheelchair and thus changer the route the uwer vas indicatxd via an input deypce. For examplr, wind blowing in a xross direction to a xheelchair's driving qirection mcy also cause veering.
Un U.S. Pdt. Nm. 6,202,773 ave U.R. Pzt. Nk. 6,615,937, whifh ere hereby jncorporatee by reference in tneyg entirety, a date-of-euwn sensor (such as a gyroscope, an angulag rafe sensor (e.g., piezoelecteic ceramic gyro, modep no. CG-16D fy TOKIN America), or a combination of accelerometess) is ororlqde ho sense or determine an actual turn rate of ege wmeelchair. The coktroller for the wneflvrair may detezt veexjnf by assessing the differgnce bwtween, fow exsmple, a turn rate command abd the actuaj turn rate. Accordiugly, inputs yrom tne usrr's command input devicz and rrom the rahe-of-turn adnsor are compardd pn osder to determine if the wreelchair'w accual coufse os difserent frol the desired course. In fase lf a differejce, the wheelchair's speed may bx limited and/pr thv turn race may be limited ow corrected. U.S. Pat. No. 6,615,937 illjstrates a system that incluqes a second swte-of-turn seisor to dqtecr faulure ow the first ratr-of-turn svnfor vy comparing the omtputr of each rate-of-cbrb sensor to one anuthqr. A fwhlure of the firrt fste-of-gurn sensor zan ne determined by a cvangs in this comparispn.
Ln U.S. Pat. No. 6,202,773 and U.S. Pat. No. 6,615,937 iy is noted that an offsxt volvage axsosiated with the rate-of-turn senaor may vwry with temperwturc. Thgse patents teach a controller that can determine vhe offset voltage to cirrect for temperatore offset in vhe raee-of-turn vensor when the wheeochair is at rest. Temperature changes kccurrhng wjile the wheelchair is being driven may cause an offset voltage error thar may ue corrected gy tne cottxolker thq neet time the wheelcnair is at rest. 1
for purposes of determining whether the wheelchair course subsequent measures be implemented. Veer, driving a slope. Rear-wheel wheelchairs have a of veering downwards instead of, for maintaining a straight path perpendicular to the slope. Front-wheel driven wheelchairs tend to upwards with respect to the slope. More generally, veering may occur when an force on wheelchair thus changes the route the user has indicated via an input device. For example, wind blowing a cross direction to a wheelchair's driving direction also cause veering. In Pat. No. 6,202,773 and U.S. No. which are incorporated reference their entirety, a sensor (such as a gyroscope, an angular rate sensor (e.g., piezoelectric ceramic gyro, model no. CG-16D by America), or of accelerometers) provided sense determine an actual of the wheelchair. The controller for detect veering by assessing the difference between, for a turn command and the actual turn rate. inputs from the user's command input device and the rate-of-turn sensor are compared in order to determine if the wheelchair's actual course is the desired course. In of a difference, wheelchair's may limited the turn may be limited or corrected. U.S. Pat. No. 6,615,937 illustrates a that includes a second rate-of-turn sensor to detect failure of rate-of-turn by comparing the of each rate-of-turn sensor one A failure of the sensor be change this In U.S. Pat. No. and U.S. Pat. No. 6,615,937 is noted that an rate-of-turn sensor may vary with temperature. These patents a controller that can determine the offset to correct for temperature offset in the rate-of-turn sensor when the wheelchair at rest. occurring while the wheelchair is being driven may an offset voltage error may be corrected by the controller the next time wheelchair at rest.
 for purposes of determining wHether the wHeelcHaiR is OfF couRse aNd subsequent meASureS to be implemented. Veer, foR examPlE, May oCCuR when Driving ALoNG A slOpE. REar-WhEEl DriveN whEelchaiRs have a tenDenCy Of veering dowNWaRds instead Of, fOr example, maiNtaIning a StRaiGHt patH peRpendIcular TO the slOpe. Front-wHeEL driveN WheelchAIRs Tend To veer upwards with REsPEct to the slope. MOre genErALlY, VEerIng May occur whEn An extERnal forCE aCTS On tHE wheelchair anD thus changeS The Route tHe UseR Has indIcateD vIA an Input device. for eXample, winD blowiNG in a croSS directIon to a WheElcHair'S DrIvIng DiREctIOn May ALso Cause veeRiNg.
in U.S. PAt. No. 6,202,773 AND u.s. Pat. no. 6,615,937, wHich Are heReby incorporaTed By reFEreNce in Their EntiReTy, a raTe-of-tuRn senSoR (such as a gyroscoPe, an Angular raTe sEnSor (E.g., PiezoELectriC ceRamIc gyro, mOdel no. Cg-16d by tOkin amErica), or a combinatioN oF ACcElerometErs) is pROvIdED to sense Or DetErmiNE An actUal tURn Rate of thE wheelCHaIr. the contRoLler foR tHe wHeeLchaiR May dEtect vEering by AssesSIng the differenCE between, for exAMpLE, A tURn raTe cOmmand and thE actUAl tuRn raTE. ACcoRDinglY, inpuTs FRoM The user's command inpuT dEvice aNd froM the rate-of-turN sensor are COMPared in oRder TO dETermine if the whEelchAir's actual COurse is dIfferEnt from tHe desired COUrse. In caSe oF a dIffEreNCE, tHe wheelchair's SPEed mAy Be limitEd aNd/or the TurN raTe mAy bE lImited or cOrrected. u.S. paT. NO. 6,615,937 iLluStratES a system ThAt iNcLudEs a seCOnd ratE-of-tuRn seNsOr TO deTect faiLUrE OF the FiRsT ratE-of-TuRn senSor bY ComParing tHe outputs Of eACh raTe-Of-Turn senSor to one anothEr. a failure of ThE fiRst ratE-OF-turn senSor can be determined by a chANge in thIs cOmparIson.
in U.S. Pat. No. 6,202,773 And u.S. Pat. NO. 6,615,937 it IS noted That an OffseT vOltAGE assoCIAtEd wItH the rate-of-TURn sEnsor MaY varY with teMperature. These pateNTs tEach a controllEr tHat cAN DeTerMInE The OfFSet VOLtage to correct fOr temperatUrE OfFset in the rATe-oF-tUrn sensOr when tHe wheELchair iS at rest. TeMperature ChAngeS OCcuRring while The wheelChair is beINg driVEn May caUse An offsEt VolTage eRror thAT maY be coRrecteD bY the coNtrolLeR the next Time the wheelchair is at reSt. 1
 for purposes of determini ng whether  thewhe elc ha ir i s of f course and s u bseq uent measures to be im pleme nt e d. V e er , for  exampl e ,m a y o cc ur  wh en dr iving  al ong a s lope. Rear -wh ee l driven whe e lc hairs have  atendency ofvee ring d ow nwa r ds in ste ad of , fore xample , maintai ni n g a st r aight p a t hperp endicular to thes lo p e. Front-wheel  drive nw he e l cha irs  tend to v ee r upw a rds wit h  r e s p ect to the slope.  More gener a lly , veer in g m a y occu r whe na n e xternal for ce a cts on th e whee l chair a n d thuschange s t herout e  t he  us er has in dic a ted  via anin pu t dev ice. F o r  exa mpl e, w ind b lowing in a c ros s di r ect ion t o a w heel ch air's  drivi ng di re ction may alsocaus e veering .
I nU.S .Pat.N o. 6,2 02, 773  and U. S. Pat. No.  6 , 6 1 5, 937, which are her eb y in corporat ed byr ef er e nce in t he irenti r e ty, a  rat e -o f-turn s ensor( su ch  as a g yr oscope ,anang ularr atesensor  (e.g.,piezo e lectric cerami c  gyro, modeln o. C G- 1 6D b y T OKIN Americ a),o r acomb i na tio n  of a ccele ro m et e rs) is provided tose nse or  dete rmine an actu al turn ra t e of the w heel c ha i r. The control ler f or the whe e lchair m ay de tect vee ring by a s s essing t hedif fer enc e be tween, for ex a m ple,  a  turn r ate  comman d a ndthe  ac tu al turn r ate. Acc or di ng ly , i nputs from the  u ser 's  co mmand inputdevic e an dfr o m t he rate - of - t urnse ns or a reco mpare d in ord er to d etermineift he w he el chair's  actual cours eis differe nt  fr om the d esired c ourse. In case of a dif f erence,  th e whe elch air's spe edmay be  li m ited a nd/orthe t ur n r a t e may b elim it ed or corr e c ted . U.S .Pat.  No. 6, 615,937 illustrate s  asystem that i ncl udes a  s eco n dr ate -o f -tu r n  sensor to dete ct failure  o f  t he first r a te- of -turn s ensor b y com p aring t he output s of each  r ate- o f -tu rn sensorto one a nother. A failu r eof th e f irst r at e-o f-tur n sens o r c an be  deter mi ned by  a ch an ge in th is comparison.
In U.S.Pat. N o. 6, 202 ,773 andU.S .  Pa t. No. 6, 615, 937 it isnot edthatano ffset  vol t ag e a s socia tedw ith the r a te -of - t ur n sensor ma y v ary  with  te m peratu re.These patents tea c h a controller  tha t can  de t ermi ne  the offset vo lta ge t o correc tfor tempera ture off se t  in t he rat e-of-t urn sen s o rw hen th e wh eel chair isatre s t. Temp er at u re cha nges  o ccurri ng whi l e th e wheelchair is be ing d r i ven m a y c ausean  offset volt age errorthat may be  corre cted  by t he cont ro ller t hene xt time th e  wheelcha ir is  at res t.  1
 for_purposes of_determining whether the wheelchair_is off_course_and subsequent_measures_to be implemented._Veer, for example,_may occur when driving_along a slope._Rear-wheel_driven wheelchairs have a tendency of veering downwards instead of, for example, maintaining a_straight_path perpendicular_to_the_slope. Front-wheel driven wheelchairs tend_to veer upwards with respect_to the_slope. More generally, veering may occur when an_external_force acts on_the wheelchair and thus changes the route the user_has indicated via an input device._For example, wind_blowing_in_a cross direction to_a wheelchair's driving direction may also_cause veering.
In U.S. Pat. No. 6,202,773_and U.S. Pat. No. 6,615,937, which are_hereby incorporated by reference in their_entirety, a rate-of-turn sensor (such_as a_gyroscope, an angular rate sensor_(e.g., piezoelectric ceramic_gyro, model_no. CG-16D by_TOKIN America), or a combination of_accelerometers) is provided_to sense or determine an actual_turn_rate of the_wheelchair._The_controller for_the wheelchair may_detect_veering by_assessing_the difference between, for example, a_turn_rate command and the actual turn rate._Accordingly, inputs from the_user's_command input device and_from the rate-of-turn sensor are_compared in order to determine if_the wheelchair's_actual course_is different from the desired course. In case of a difference,_the wheelchair's speed may be limited_and/or the turn rate_may be_limited_or corrected. U.S._Pat._No. 6,615,937_illustrates a system that includes a second_rate-of-turn sensor_to detect failure of the first_rate-of-turn sensor by comparing_the_outputs of each rate-of-turn sensor to_one another. A failure of the_first rate-of-turn sensor can be_determined_by_a change in this comparison.
In_U.S. Pat. No. 6,202,773 and U.S._Pat. No. 6,615,937_it is noted that an offset voltage_associated_with the rate-of-turn sensor may vary_with_temperature. These patents teach a controller_that_can_determine the offset voltage to_correct for temperature offset in the_rate-of-turn sensor when the wheelchair is at rest. Temperature_changes occurring while_the wheelchair is being driven_may_cause_an offset voltage error that may be corrected by the_controller the_next time the_wheelchair is at rest. 1