the following is a detailed description of the presently known modes of carrying out the inventions . this description is not to be taken in a limiting sense , but is made merely for the purpose of illustrating the general principles of the inventions . the present invention discloses a driven monitoring device , attached onto a continuous passive motion exercise system , with the functions of measuring the driving force f or torque τ from a driving device d to a mounting device 4 , 8 through force or torque sensors s , calculating joint viscosity and stiffness parameters , and detecting joint muscle active contraction . thus the status changes of muscle stiffness and joint viscosity can be evaluated and the possibility of secondary injury can be reduced during joint rehabilitation periods . the schematic diagram of the present invention applied on a knee join exercise mechanism with continuous passive operation is illustrated in fig1 . the exercise mechanism comprises a mounting device 4 having a flexing and extending mechanism and a fastening device 3 , a driving device d providing a driving force f and a driven monitoring device dmd . the flexing and extending mechanism disposed on a ground 2 contains two levers , a horizontal sliding block 5 , and a hinge set 6 . the two levers are jointed together by one hinge of the hinge set 6 while the other two ends are pivotally jointed to the horizontal sliding block 5 , and the ground 2 , respectively . the horizontal sliding block 5 can slide horizontally and straight with respect to the ground 2 . the driving force f , applied on the horizontal sliding block 5 , can bring the block 5 back and forth to perform straight and horizontal reciprocative movement so as to conduct reciprocative angular displacement motion of the flexing and extending mechanism . through a fasting device 3 on the mounting device 4 , a lower limb 1 of a patient is fastened onto the mounting device 4 . in this embodiment of the present invention , the exercise mechanism , being mounted on a bed or on the ground 2 , therefore , forms a one degree - of - freedom mechanism capable of flexing and extending the knee joint of the lower limb 1 repeatedly . and the driving force f continuously drives the mounting device 4 and the lower limb 1 so as to perform knee - joint continuous passive motion exercise . fig2 illustrates the schematic diagram of the present invention applied on an elbow joint continuous passive motion exercise mechanism . such an exercise mechanism comprises a mounting device 8 , a hinge 10 and a driving device generating driving torque τ . an upper limb 9 of a patient is fastened through a fastening device 7 onto the mounting device 8 . the mounting device 8 contains two levers ; and the two levers are jointed by the hinge 10 . a driving torque τ on the hinge 10 repeatedly rotate one lever with respect to another clockwise and counterclockwise . thus , the exercise mechanism forms a one degree - of - freedom mechanism capable of flexing and extending the elbow joint through the driving torque τ . as the driving torque τ continuously applied on the hinge 10 , the two levers rotate with respect to each other in a clockwise - counterclockwise movement , and the elbow - joint continuous passive motion exercise is performed . patients utilize the continuous passive motion exercise systems shown in fig1 or fig2 to bring joints to motions through an external force or torque , without active contracting his or her own muscles . therefore , not only that the injured muscles are to recover through much needed rest , but the result that the joint tendons and muscles are to be sticky and stiff due to the lack of exercise can also be prevented ; in addition , through twisting and turning of joints , joints are to obtain necessary lubrication and nutrients , thus preventing joints from atrophy . yet when patients are in such rehabilitation therapy sessions , it is the fear , both for pain and for possible secondary injury due to muscle weakness and stiffness , which leads to the angles of joint motions being confined within a small range , or the progress of rehabilitation being slowed down . according to the embodiments of the present invention , a continuous passive motion exercise system comprises a driven monitoring device dmd , having force or torque sensors s corresponding to the exercise mechanism , so as to monitor the driving force f or the driving moment τ needed to perform continuous passive motion exercises , wherein f or τ is a vector with the dimension being identical to that of the degree of freedom of the mounting device 4 , 8 . in one more aspect of the present invention , the driven monitoring device dmd comprises a data recorder dr to record and a data transceiver tr interface to receive from and transmit to external data ed storing and / or analyzing devices m the associated values of the predetermined reciprocative motion pattern , numbers of cycles , said averages , duration of use , and patient &# 39 ; s id , for future analysis and evaluation . the one degree - of - freedom exercise system shown in fig1 is to be utilized for illustrating the rehabilitation system . at first , to model the mechanics system of the bone - muscle system of a joint under passive motion , two kinds of internal forces can be defined ; one is conservative elastic force ( such as spring force with an elastic coefficient k ) from the conservative elastic force member 12 a , and the other non - conservative force ( such as viscosity , friction , etc . with a damping coefficient c ) from the non - conservative force member 12 b as illustrated in fig3 . therefore , the mechanics model of the rehabilitation system shown in fig1 , providing both thigh and leg are fastened on the two levers 13 of the mounting device 4 , can be shown as in fig4 , wherein m t is the equivalent mass of the thigh and the lever whereon the thigh is fastened , m l is the equivalent mass of the leg and the lever whereon the leg is fastened ( a foot is regarded as part of the leg ), θ n and θ h are the angular displacement vector of the knee joint and the hip joint respectively with the assumption of no relative motion between a limb and its mounting device , point a is a reference point fixed in the horizontal sliding block 5 which can only move straightly and horizontally with respect to the ground 2 , x is the displacement vector of point a with respect to the ground 2 , k n is the effective coefficient of elasticity for the total passive conservative elastic force stored in the knee joint muscles and tendons , τ n is the friction moment vector generated on the center of rotation of the knee joint , k h is the effective coefficient of elasticity for the total passive conservative elastic force stored in the hip joint muscles and tendons , and τ h is the friction moment vector generated on the center of rotation of the hip joint . it is assumed that k n is a function of τ n only and k h is a function of θ h only . both k n and k h have nothing to do with the directions and the velocity of their associated joint motions . thus , ( k n θ h + c n ) is the total conservative elastic force when the knee joint muscles and tendons are passively brought to an angular displacement τ n ; wherein c h is a constant . and ( k h τ h + c h ) is the total conservative elastic force when hip joint muscles and tendons are passively brought to an angular displacement θ h , wherein c h is a constant . according to the embodiments of the present invention , during a cycle of passive reciprocative motion , the amount of work ( w f ) done by the horizontal driving force vector f equals to wherein w d represents the work done by the total friction of the mechanism , w n represents the work (∫ τ n · dθ n ) done by the knee joint friction moment vector τ n , w h represents the work (∫ τ h · dθ h ) done by the hip joint friction moment vector τ h , and the total amount of work from the gravitational force and / or other conservative elastic forces in one complete cycle of motion is zero . assuming in each cycle of a passive reciprocative motion , the displacement and velocity patterns of the mounting device are all to be kept the same . then w d in each cycle can be regarded as identical ( assuming the operational environment including temperature and humidity and the mass of the leg portion pose little alteration or impact ). therefore , between two complete cycles of passive reciprocative motions , the difference regarding the amounts of the work done by the horizontal driving force f is as follows : δ w f =− δ ( w d + w n + w h )=− δ ( w n + w h ) ( 2 ) wherein δ is the operand for the difference obtained from the latter value minus the former value . hence , δw f reflexes only the change in the work done by joint friction . since the motion path of two cycles are the same , δw f represents the change in joint friction between two cycles . in the present invention , δw f can be divided by the total displacement distance 2l during one cycle of passive motion , wherein l represents the farthest horizontal distance that the reference point a moves with respect to the ground in one cycle , so as to define the variation of the average joint friction force δf b . therefore , when the joint friction becomes smaller , index δf b shall become positive . a negative value of δf b thus , indicates the increase of the joint friction . therefore , regarding the system of the present invention , when passive reciprocative motions proceed under extremely repeatable speed , the driven monitoring device then measures the driving force f , so as to calculate and monitor the amount of variation of the average joint friction force δf b during the rehabilitation process , and thus obtains the state of variation regarding the joint friction and viscosity . since the joint friction force might be very minute compared to the other force sources involved , to monitor the variation of such joint friction , the present invention averages the w f value of a plurality of cycles ( such as 1000 cycles ) of passive reciprocative motions with identical displacement and velocity patterns and compare these averages recorded the same way in different rehabilitation sessions to observe the state of variation of the agility of joints . in such a way , the possible noise caused by the variations of the rehabilitation system and environment can be reduced . furthermore , the strength of elasticity regarding muscles and tendons at joint is also one of the indices for joint rehabilitation . considering the system shown in fig1 , in half of a complete cycle of passive reciprocative motion such as the flexing motion cycle , based on the principle of work , the equation can be written as w f ( i ) + w jk ( i ) + w mk ( i ) + w mf ( i ) + w gf ( i ) + w jf ( i ) = 0 ; i = 1 , or 2 ( 3 ) where variables with subscript ( 1 ) or ( 2 ), respectively denote their values at the first or the other half cycle of passive reciprocative motion which originates from one end position with zero velocity and ends at the other end position with zero velocity ; and w jk ( i ) , w mk ( i ) , w mf ( i ) , w gf ( i ) , and w jf ( i ) denote the work done by conservative joint elasticity force , conservative machine elasticity force , machine friction force , gravitational force , and knee - and - hip joint friction force respectively in the i - th half cycle . by subtracting w f ( 1 ) from w f ( 2 ) , the following equation is obtained as w f ( 2 − 1 ) =( w jk ( 1 ) − w jk ( 2 ) )+( w mk ( 1 ) − w mk ( 2 ) )+( w mf ( 1 ) − w mf ( 2 ) )+( w gf ( 1 ) − w gf ( 2 ) )+( w jf ( 1 ) − w jf ( 2 ) ) ( 4 ) wherein w f ( 2 − 1 ) is defined as ( w f ( 2 ) − w f ( 1 ) ). as described above , if the displacement and velocity patterns for the motion of the mounting device to be identical and the change in the mechanic characteristics of the machine are maintained to be very small and negligible during each cycle of a reciprocative passive motion , each ( w gf ( 1 ) − w gf ( 2 ) ), ( w mk ( 1 ) − w mk ( 2 ) ), and ( w mf ( 1 ) − w mf ( 2 ) ) value can be regarded as identical in each cycle . therefore , the difference of w f ( 2 − 1 ) between two cycles of motion can be obtained as follows : δ w f ( 2 − 1 ) = δ ( w jk ( 1 ) − w jk ( 2 ) )+ δ ( w jf ( 1 ) − w jf ( 2 ) ) ( 5 ) assuming that the change of a human joint friction with respect to time is independent of the direction of the joint rotation , then the term δ ( w jf ( 1 ) − w jf ( 2 ) ) equals to zero . therefore , the equation can be written as since w jk ( i ) , i = 1 or 2 , is a work done by a conservative force , w jk ( 2 ) is equal to − w jk ( 1 ) . hence , the equation becomes since w jk ( 1 ) is dependent on the initial and the end positions of the first half cycle of a reciprocative passive motion only , if the two positions are chosen so that w jk ( 1 ) is equal to zero , it is possible that the effect of elasticity change in joint will not be shown in the above equation . in such cases , a different initial position or a different end position should be chosen . however , δw jk ( 1 ) along is not enough to determine whether the elastic force is increasing or decreasing , thus the sign of w jk ( 1 ) has to be known to correctly interpret the result . when w jk ( 1 ) is positive , the potential energy due to the conservative elastic force of the joint in the first half cycle is increasing . a positive δw jk ( 1 ) then means that the average elastic force is increasing , hence the average stiffness is increasing , and vice versa . when w jk ( 1 ) is negative , the potential energy due to the conservative elastic force of the joint in the first half cycle of the joint is decreasing . a positive δw jk ( 1 ) means that the average elastic force is decreasing , hence , the stiffness is decreasing , and vice versa . eqn . ( 4 ) can be rewritten as , ( w jk ( 1 ) − w jk ( 2 ) )− w f ( 2 − 1 ) −( w mk ( 1 ) − w mk ( 2 ) )−( w mf ( 1 ) − w mf ( 2 ) )−( w gf ( 1 ) − w gf ( 2 ) )−( w jf ( 1 ) − w jf ( 2 ) ) ( 8 ) by running the same reciprocative motion without any limb mounted onto the machine and assuming the term ( w mf ( 1 ) − w mf ( 2 ) ) is either close to zero or has little to do with or without a limb mounted , the following equation can be obtained w f0 ( 2 − 1 ) = w f0 ( 2 ) − w f0 ( 1 ) =( w mk ( 1 ) − w mk ( 2 ) )+( w mf ( 1 ) − w mf ( 2 ) )+( w gf0 ( 1 ) − w gf0 ( 2 ) ) ( 9 ) where w f0 ( i ) , w gf0 ( i ) ; i = 1 or 2 is the work done by the driving force , and the gravitational force on the machine , respectively without any limb mounted in the i - th half cycle . from eqns . ( 8 ) and ( 9 ) and assuming w jf ( 1 ) = w jf ( 2 ) , the equation can be written as 2 w jk ( 1 ) = w f ( 2 − 1 ) − w f0 ( 2 − 1 ) − 2 w gfb ( 1 ) ; ( 10 ) where w gfb ( 1 ) is the work done by the gravitational force on the limb in the first half cycle and can be calculated from the configurations of the limb at the two end positions in a half cycle of a reciprocated motion . hence , from eqn . ( 10 ), the sign of w jk ( 1 ) can be determined . through combining eqn . ( 7 ) and eqn . ( 10 ), the average change of the joint elastic status between the two cycles can be defined as δ w k = w jk ( 1 ) δw f ( 2 − 1 ) /( 2 ×| w jk ( 1 ) |) ( 11 ) in the embodiments of the present invention , when δw k is positive , the average internal elastic force of the joint is increased . it represents that the degree of rigidity for the joint muscles and tendons is to become larger , and vice versa . therefore , a variation of the agility of joints which can be obtained through the driven monitoring device has developed to better understand the effect of a rehabilitation session . regarding the system of the present invention , δw k can be divided by the length l , the travel distance of point a in the half cycle of passive reciprocative motion , and obtain the amount of variation for the average elastic force f k as follows : δ f k = w jk ( 1 ) δw f ( 2 − 1 ) /( 2 l ×| w jk ( 1 ) |) the driven monitoring device then is capable of comparing the impact during the rehabilitation processes regarding the elasticity of joint muscles in every time or every day by utilizing δf k calculated . the comparative index values regarding agility and elasticity are suitable for the comparison of variation between two cycles of motion with identical displacement , velocity . in overall terms of rehabilitation , the range of motion , the displacement and velocity should be properly adjusted or altered . therefore , when the embodiments of the present invention are to compare the effect of the rehabilitation session from certain periods or the overall process , the user can adjust the displacement and velocity of the exercise mechanism back to the setup that is intended to compare , then the driven monitoring device may proceed to the effect assessment . all the evaluations of the embodiments above presuppose that the joint muscles do not perform active contractions to produce tension . in another embodiment of the present invention , the driven monitoring device further comprises a data recorder capable of storing a sequence of reference values of the driving force f at different sampling positions and orientations during motions . such values are obtained when the joint muscles of patients do not contract actively . the average of all the values at the same sampling position and orientations in different cycles for the first several cycles is used to represent the reference value of the driving force f at the same sampling position and orientation during a continuous passive motion session . an offset is set up in the driven monitoring device , which continuously monitors whether the absolute value of the difference between the driving force f value and the corresponding reference value at the same position and orientation during the cycles of motion is to exceed the offset ; if so , muscles might have actively contracted ( such as muscle contraction due to pain ). joints after surgeries are to be more frail than those under normal conditions , and muscles are also under recovering condition , therefore , excessive pulling or squeezing might cause muscle tear or joint dislocations . the present invention provides an exercise system with the automatic safety control function ( such as stopping the system operations ), thus preventing patients from possible secondary injuries . the system of the present invention can also set up several offsets so that more proper reactions can be performed during rehabilitation sessions ( such as receding back or slowing down the exercise motion .) in addition , since rehabilitation sessions might take tremendous length of time , medical personnel or patients themselves cannot record and monitor the rehabilitation indices at all time , and during the rehabilitation session , large amount of data are needed to be stored , so as to conduct analyses , follow - ups and display . therefore , the system of the present invention has a data recorder , through which detailed measurement and calculated data are to be recorded during the rehabilitation sessions and then transmitted to other devices to be stored , thus enabling medical personnel or patients to perform more precise analyses , long - term follow - ups and statistics . meanwhile , when the system of the present invention is utilized by several patients , the set - ups of the machine can easily be retrieved to fit the need of every patient . by the same token , regarding the present invention and other devices , persons skilled in the art are able to make proper variations based upon the calculation methods disclosed herein so as to obtain the effects and characteristics of the invention . although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof , those skilled in the art can easily understand that all kinds of alterations and changes can be made within the spirit and scope of the appended claims . therefore , the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein .
the continuous passive motion exercise system enables human &# 39 ; s joints to recover speedily to original functioning after injuries or surgeries , and thus shortens the period of time needed for joint rehabilitation . the present invention provides a force or torque monitoring device attached onto a continuous passive motion exercise mechanism to measure the driving force of the repeated joint flexing and extending motion , so as to evaluate the change of the viscosity and the stiffness of the injured joints through different rehabilitation periods . this monitoring device also monitor degrees of joint muscle &# 39 ; s active contraction and thus slows down or stops the repeated motions of exercise mechanisms to improve safety concerns . in addition , such a monitoring device also includes a data transceiver interface utilized for transmitting and receiving the information regarding a patient &# 39 ; s states of using such a exercise system in order to assess the patient and to provide doctors with the basis for evaluating and improving the rehabilitation condition of the injured joints .