Patent Abstract:
a body weight support system that monitors and controls the level of support force within a stepcycle to result in normative center of mass movement and ground reaction forces . the system comprises a harness connected to a lift line which in turn is connected to a means for advancing and retracting the lift line . a control system is configured to monitor load on the cable and to regulate lift line advancement and retraction in response to load information . the support system can be combined with a treadmill for locomotor training of a subject .

Detailed Description:
referring to a particular embodiment in fig1 , a user wears a suitably modified parachute harness 2 that is attached to an overhead cable 4 . the cable in turn runs vertically up over a pulley 6 and attaches to a double rod control cylinder 8 . when pressure is supplied to the cylinder via a compressed air / gas / hydraulic supply ( not shown ), the cylinder compresses . this cylinder compression via the overhead cable creates an upward force applied to the subject . the upward force can be regulated by supplying or exhausting air , gas or hydraulic fluid to or from the cylinder . in preferred embodiments , the cylinder is operated with compressed air / gas . a load cell 10 is placed in series with the cable 4 . the load cell sends feedback about the subject &# 39 ; s present level of support force to a computer 12 . a computer program continually compares the present level of support force to a manually selected desired level of support force . information from the computer is sent to an electrical pneumatic / gas / hydraulic control valve 14 . the electrical pneumatic / gas / hydraulic control valve 14 will modify the amount of flow into and out of the cylinder depending on whether the present level of support is greater than or less than the desired level . the cylinder 8 is mounted on an adjuster plate 16 that is slidably connected to a guide track 18 which is mounted to a frame 19 . the sliding adjuster plate 16 is moved by a servo motor 20 that sends feedback to and receives control from the computer 12 . by mounting the cylinder 8 to the sliding adjuster plate 16 the position of the cylinder can be moved . this has several advantages . first the cylinder can be positioned during walking , running and standing situations to maximize the range of motion allowed by the subject . second , the cylinder can be moved such that the cable will extend towards the ground far enough to easily allow a patient in a wheel chair to be attached to the overhead support . once the seated subject is attached , the cylinder can be moved back to raise the subject from a seated position to a standing position . in practice , the sliding adjuster plate 16 can be physically locked into its required position . when used in this manner , the servo motor 20 initially positions the sliding adjuster plate but is not part of the control loop thereafter . in other situations , the sliding adjuster plate can move and be part of the control loop . once the computer 12 is operational , the electronic control valve 14 will apply pressure to the control cylinder 8 , moving the piston in the appropriate direction until the center position is reached ( this is the position where the control cylinder 8 will have the maximum range of motion during walking or running ). after this event , the control cylinder 8 is locked in place and the servo motor 20 is commanded to extend such that the control cylinder 8 is positioned as required to enable the cable 4 to be clipped into the support harness worn by the user . once the user is properly positioned , the servo motor 20 can be activated to slowly erect the user to the desired standing position — this is the position where the desired level of support is read by the load cell 10 . an adjustable relief valve 22 can be set to ensure that the user is protected from surges that may arise . the desired percent of support weight can then be input to the computer 12 , which will then obtain feedback from the load cell 10 and the electronic control valve 14 to achieve the desired result . at this time the control cylinder 8 can be unlocked allowing it to move in the appropriate directions to achieve the appropriate support levels . limit switches 24 and 26 can be used to alert the computer when the endpoints of the control cylinder are being approached , at these events the servo motor 20 can be used to re - position the control cylinder 8 so that the center of the range of motion during walking or running moves closer to the midpoint position of the control cylinder 8 . a treadmill 28 can then be commanded as required and the user can begin stepping . the system continually monitors the load cell 10 and makes adjustments via the electronic control valve 14 . a first stop 30 is a dampened “ soft ” stop providing a cushioned deceleration in the event of any failure in the sliding mechanism / attachments . a second stop 32 providing deceleration in the opposite direction can be spring loaded . in accordance with particular embodiments , a secondary control loop and associated software is utilized whereby the servo - motor 20 can attempt to adjust for positional changes to compensate for a patient slowly moving toward the ground ( which among other factors , affects the forces on the patients feet ), or to compensate for changes in desired body weight support levels which exceed the limit in such changes inherent to the length on the control cylinder 8 . it can do so by manipulating the sliding adjuster plate 16 . the computer 12 can compensate for the cylinder position by adjusting the pressure appropriately . if necessary , the computer can either slow or stop the treadmill motion . during this correction the subject would be gently lifted back to the required position . the advantages of this set up are an automatic and smooth correction of therapy without the need for additional therapists to lift and readjust the patient . a pressure sensor 34 can be monitored for the rate of change of pressure levels and for safety . in particular embodiments , the pressure sensor can be placed within the control cylinder 8 to send information about cylinder pressure to the computer 12 . the computer 12 can receive feedback from the load cell 10 and / or the pressure sensor 34 and regulate support force accordingly . the pressure sensor can act as a comparator ( check and verify ), or as a supplement to the load cell readings . preferably , the pressure sensor is a pressure transducer . in the embodiment of fig1 , the control cylinder 8 is mounted horizontally to the treadmill surface . alternatively , the cylinder can be mounted vertically , with the cable 4 running horizontally over a second pulley and attaching to the vertical cylinder . also , the control cylinder 8 can be mounted directly to the servo motor 20 without the use of the adjuster plate 16 . the control cylinder in fig1 is a double - rod cylinder . alternatively , the control cylinder can be a single rod cylinder or a rod - less cylinder . in further embodiments , the control cylinder can be replaced with an “ artificial muscle ”. as is well known in the art , an “ artificial muscle ” employs an approach to precise and repeatable linear displacement technology using the concept of material deformation and flexure to achieve linear motion . the basic concept involves the wrapping of a watertight , flexible hose with non - elastic fibers arranged in a rhomboidal fashion . this results in a three - dimensional grid pattern , and when compressed air is introduced into the system , the grid pattern is deformed . a pulling force is generated in the axial direction , resulting in a shortening of the “ muscle ” as internal pressure is increased . in other embodiments , the servo motor 20 can be replaced with a fluid - operated cylinder for moving the adjuster plate 16 . preferably , the fluid - operated cylinder is a pneumatic cylinder or a hydraulic cylinder . control algorithms can regulate the pressure of the fluid - operated cylinder to contribute to the regulation of the forces exerted on a user . for additional flexibility and safety , a treadmill controller 36 and an emergency stop 38 for the treadmill can be added to the system . in particular embodiments , the limit switches can be replaced with a linear transducer . additionally , a direct drive means can replace the compressed air / gas / hydraulic part of the system . the present invention may be better understood by referring to the accompanying example involving a specific embodiment of this invention . this example is intended for illustration purposes only and should not in any sense be construed as limiting the scope of the invention as defined in the claims appended hereto . this example is a comparison of body weight support systems . locomotor training using body weight support ( bws ) on a treadmill and manual assistance has emerged as a potential rehabilitation intervention for the recovery of walking following spinal cord injury ( sci ). the success of this approach is dependent on providing appropriate sensory cues to the spinal cord by simulating the kinetics and kinematics of over - ground walking . several different bws systems have been used to accomplish the unweighting component of this training ( i . e ., a winched rope , a pneumatic lift , stretched springs or counter - balanced weights ). the type of bws system used in locomotor training may affect ground reaction forces ( grf ) and center of mass ( com ) movement during gait which in turn could modulate afferent information . the purpose of this study was to compare the effects of two bws systems , a position control system and a open — loop force control system , on limb loading , ( com ) movement and motor control during locomotor training . two non - disabled ( nd ) and two clinically complete ( see reference 18 ) sci subjects participated in the study . informed consent was obtained from all subjects and the experiments were approved by the university of california , los angeles human subjects protection committee . ground reaction forces ( grf ) were collected during stepping using pressure sensing insoles . bws force was collected from a force transducer placed in series with the bws system cable . center of mass ( com ) movement was estimated from 6 dimensional recordings of pelvis movement . three different bws systems were used to support the subject &# 39 ; s body weight during locomotion : 1 ) position control system ; 2 ) open — loop force control system ; 3 ) closed — loop force control system . emg data was collected from lower limb muscles . all subjects stepped on a treadmill at a range of speeds ( 0 . 5 - 1 . 34 m / s ) and levels of bws ( 0 - 100 % body weight ) on both the position control system and the open — loop force control system . sci subjects were provided with manual assistance as needed . com movement , grf , bws force and emg were analyzed . following the analysis , a dynamic force control bws system was designed to minimize any fluctuations in bws force during locomotion . one of the nd subjects repeated the procedure on the closed — loop force control system . restricts vertical com movement . stiffness of system results in large fluctuations in bws force and loss of heel strike and toe - off peaks . allows vertical com movement similar to over - ground locomotion . bws force fluctuates with com movement . grf had both heel strike and toe - off peaks , however heel strike peaks were higher and toe - off peaks were lower than expected . allows vertical com movement similar to over - ground locomotion . of the three systems it showed more control of fluctuations in bws force during locomotion . grf showed distinct heel strike peak , toe - off peak , and unloading at midstance . amplitude of all three of these components were comparable to over ground gait adjusted for bws . d . the interaction between the bws systems and com movement / grf occur for both the nd and sci subjects . e . kinetics and kinematics during locomotor training become more comparable to over - ground walking as deviations in bws force during gait are controlled and minimized . 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