Motorized wheelchairs

Abstract

A motorized wheelchair is advantageously provided with a rate-of-turn feedback sensor and with forward/reverse motion, lateral motion, and vertical motion acceleration feedback sensors that are integrated into a closed-loop wheelchair servo control system to differentially control the rotational speed of wheelchair opposed motor-driven wheels and thereby obtain improved wheelchair motion stability through reduction/elimination of likely wheelchair spin-out and wheelchair tipping during wheelchair operation.

What is claimed is:  
     
         1 . In a motorized wheelchair assembly, comprising: 
 a wheelchair chassis;    a motor-driven right wheel connected to and providing rolling support for said wheelchair chassis;    a motor-driven left wheel connected to and providing rolling support for said wheelchair chassis;    a castor subassembly connected to and providing rolling support for said wheelchair chassis;    an input device which generates wheelchair chassis turn direction command signals and a wheelchair chassis linear velocity command signals in response to wheelchair operator manipulation; and    a closed-loop controller subassembly receiving command signals from said input device and generating output control signals that regulate the rotational speeds of each of said motor-driven right and left wheels in response to differences between said input device turn direction and linear velocity command signals and detected wheelchair chassis actual turn directions and actual turn rates.    
     
     
         2 . The motorized wheelchair assembly invention defined by    claim 1   , wherein said closed-loop controller subassembly incorporates an angular rate of turn sensor, wherein said closed-loop controller detects signals from said angular rate of turn sensor which correspond to actual turn directions and turn rates of said wheelchair chassis, and wherein said motor-driven right and left wheels are positioned ahead of said castor subassembly in the direction of motorized wheelchair assembly forward motion.  
     
     
         3 . The motorized wheelchair assembly invention defined by    claim 1   , wherein said controller subassembly includes an angular rate-of-turn sensor that is orthogonally supported by said wheelchair chassis, and that detects wheelchair chassis actual turn direction and actual turn rate.  
     
     
         4 . The motorized wheelchair assembly invention defined by    claim 3   , wherein said controller subassembly angular rate-of-turn sensor is a piezoelectric ceramic gyroscope.  
     
     
         5 . The motorized wheelchair assembly invention defined by    claim 3   , wherein said controller subassembly angular rate-of-turn sensor is a rotating gyroscrope.  
     
     
         6 . The motorized wheelchair assembly invention defined by    claim 3   , wherein said controller subassembly angular rate-of-turn sensor is located remote from but in feedback signal-communicating relation with said controller subassembly.  
     
     
         7 . The motorized wheelchair assembly invention defined by    claim 4   , wherein said controller subassembly averages the output feed-back signal of said piezoelectric ceramic gyroscope when said wheelchair assembly is not in motion, and utilizes the average output feedback signal of said angular rate-of-turn sensor as a signal-processing correction value when generating said controller subassembly output control signals.  
     
     
         8 . The motorized wheelchair assembly invention defined by    claim 1   , wherein said controller subassembly further includes forward, lateral, and vertical linear acceleration sensors that are orthogonally supported by said wheelchair chassis and that detect wheelchair chassis actual forward tilt and actual lateral tilt to thereby establish a wheelchair turn rate control limit and a wheelchair linear velocity control limit.  
     
     
         9 . The motorized wheelchair assembly invention defined by    claim 1   , wherein said controller subassembly further includes forward and vertical linear acceleration sensors that are orthogonally supported by said wheelchair chassis and that detect wheelchair chassis actual forward tilt to thereby establish a wheelchair linear velocity control limit.  
     
     
         10 . The motorized wheelchair assembly invention defined by    claim 1   , wherein said controller subassembly further includes lateral and vertical linear acceleration sensors that are orthogonally supported by said wheelchair chassis and that detect wheelchair chassis actual lateral tilt to thereby establish a wheelchair turn rate control limit.  
     
     
         11 . In a method of controlling motion of a motorized wheelchair assembly having separately-controlled, motor-driven right and left wheels that provide wheelchair assembly rolling support, the steps of: 
 providing turn direction command inputs and turn rate command inputs to the motorized wheelchair assembly to cause correlated wheelchair motion;    sensing the actual turn direction and actual angular rate-of-turn of said motorized wheelchair assembly;    comparing said sensed wheelchair assembly actual turn direction and angular rate of turn signals with wheelchair assembly provided turn direction and turn rate command inputs and developing their respective differences as control signals; and    utilizing said developed control signals to regulate differential rotation of said motorized wheelchair assembly motor-driven right and left wheels to thereby limit wheelchair actual rate-of-turn magnitude to a predetermined magnitude not exceeding the magnitude of said wheelchair assembly turn rate command input.    
     
     
         12 . The method invention defined in    claim 11   , wherein said sensing step is accomplished gyroscopically.  
     
     
         13 . The method invention defined by    claim 11   , wherein said sensing step involves sensing said actual turn direction and said actual rate-of-turn of said motorized wheelchair assembly while said wheelchair assembly is at rest and utilizing the so-sensed turn direction and rate-of-turn as correction values during subsequent sensing of said actual turn direction and actual rate-of-turn of said motorized wheelchair assembly.  
     
     
         14 . The method invention defined by    claim 11   , and further comprising: 
 sensing motorized wheelchair assembly forward deceleration rates;    comparing said sensed forward deceleration rates to a permissible deceleration rate based on wheelchair angle of actual wheelchair forward tilt, and developing their respective differences as control signals; and    utilizing said developed control signals to regulate differential rotation of said motorized wheelchair assembly motor-driven right and left wheels to thereby limit wheelchair actual rate-of-turn magnitude to a predetermined magnitude not exceeding the magnitude of said wheelchair assembly permissible deceleration rate.