Modelling and Control of FES-Assisted Indoor Rowing Exercise

Transcription

1 Moelling an Control o FS-ssiste Inoor Rowing xercise Z. ussain, M. O. Tokhi, S. Gharooni an S.F. Toha Department o utomatic Control an System ngineering The University o Sheiel, U ( cop6zh@sheiel.ac.uk bstract: This paper presents the evelopment o a moel o inoor rowing exercise or paraplegics. Inoor rowing exercise is introuce as a hybri exercise or restoration o unction o lower extremities or paraplegics through the application o unctional electrical stimulation (FS. Two stimulate muscle moels, quariceps an hamstrings, are evelope or knee extension an lexion. uzzy logic control strategy is esigne to control the rowing manoeuvre. Simulation results veriying the control strategy are presente an iscusse. eywors: Inoor rowing exercise, Paraplegics, Muscle moel, Fuzzy logic control.. INTRODUCTION Paraplegic is a person who has complete paralysis o the lower hal o the boy incluing both legs, usually cause by amage to the spinal cor. Frequent causes o amage are trauma (car accient, gunshot, alls, etc. or isease (polio, spina biia, etc.. It prevents them rom walking, staning an moving reely, thereore reuces the quality o lie an leas to severe psychological an physiological eects. Paraplegics are at increase risk o Cariovascular Disease, Type 2 Diabetes Mellitus an Obesity (Wheeler, et al., 22; Raymon, et al., 999; nrews, et al., 995. To reuce these risk actors, a high intensity physical activity is require through the application o Functional lectrical Stimulation (FS. FS aims to generate movements or unctions which mimic normal voluntary movements an restores the unctions which those movements serve (Massou, 27. FS-assiste inoor rowing exercise is the hybri FS activity introuce as a high intensity, eective, sae, aorable an natural alternative or total boy exercise that combines FS-assiste lower boy movement with voluntary upper boy movement (Davooi, et al., 2, 22a, b, c. In FS-assiste inoor rowing exercise, FS is applie to the muscles or extension an lexion o hip, knee an ankle in orer to perorm the rowing exercise. The evelopment o well oune physiological base muscle moel is important in obtaining smooth rowing manoeuvres. Many muscle moels have been create an one o the earliest an perhaps most popular employe muscle moel is the ill moel. Various moiications have been mae to more accurately incorporate urther complexities an increase the moel s accuracy. One o the most notable muscle moels was evelope by Riener (Riener, 999; Riener, an Quintem, 997; Riener, an Fuhr, 998; Riener, et al., 996, 999, 2. The moel escribes the physiologically base interpretation an inclues muscle atigue an calcium ynamics. The moel is compose o three parts, namely muscle activation, muscle contraction an boy segmental ynamics. Muscle activation provies the activation neee by the muscle to generate orce. Muscle contraction is escribe as a orce generating properties erive by scaling a generic ill base moel whereas, the boy segmental ynamics consier the passive muscle properties an equation o motion with the interaction o environment. To achieve a smooth an well coorinate rowing exercise or paraplegics, a well structure control strategy is require. Davooi et al. (22c evelope a controller that automatically controls the electrical stimulation o the paralyze leg muscles to perorm the lower boy part o the rowing manoeuvre with coorination to voluntarily perorm the upper boy part o the manoeuvre. lthough a smooth rowing manoeuvre was obtaine, the total stimulation per cycle was high. The control strategy o FS-assiste inoor rowing exercise becomes more iicult as it involves a complex physiological base human muscle. The complexity o the motor system o the human muscle leas to a egree o uncertainty in a evelope mathematical moel or the muscle. Few control strategies teste in this stuy inclue (moel-base PID control, an the results are not very impressive, ue to such uncertainty in the moel. Fuzzy logic control (FLC is thus purpose as it oes not require a moel o the system. In this paper, FLC is evelope to regulate the electrical stimulation applie to the physiological base muscle moel or FS-assiste inoor rowing exercise or restoration o unction o lower extremities. 2. DSCRIPTION OF MODL 2. Inoor Rowing xercise Moel. The inoor rowing exercise moel comprises o two parts, inoor rowing machine an humanoi moel evelope using the Visual Nastran sotware. The machine is esigne base on the moiie inoor rowing machine (Fig. that comprises o all basic parts o the real machine. new seating system was evelope which has high back,

2 ajustable backrest an ajustable belt to stabilize the trunk. mechanical braking system is mounte beneath the seat an integrate to the pull phase o the rowing cycle to prevent lower extremities collapse. Two ajustable saety stops were installe on the rail an two springs installe on the seat to limit motion or knee joint protection against hyperextension an hyperlexion. Two groups o mono-articular muscles or knee extensor (quariceps an lexor (hamstrings are evelope. The muscle moel evelope is compose o three parts, namely muscle activation, muscle contraction an boy segmental ynamics. The muscle activation moel comprises our main components: non-linear recruitment characteristic, requency characteristic, calcium ynamics an muscle atigue (Fig.3. (u 2 RecruitmentCharacteristic (u FrequencyCharacteristic Prouct.9s 2+.6s+ CalciumDynamics acal aat Muscle Fatigue -C- Time Delay ct Fig.3 Muscle activation moel T_el Fig.. Moiie inoor rowing machine humanoi moel was esigne base on the anthropometric ata obtaine rom Winter (99. The humanoi moel evelope in this work is base on human boy whose height is.7m an weight is 65kg. Symmetrical property o the boy segment is important to ensure that segments on either sie o the humanoi are positione symmetrically aroun the sagittal plane. The inal stage o the evelopment o the inoor rowing exercise moel is to combine the humanoi moel into the machine. It is important to ensure that the humanoi moel is attache to the inoor rowing machine moel at the right position. Since the movement o the humanoi moel is symmetrical between let an right boy, the trunk o the humanoi moel has to be positione in the mile o the seat. The complete moel o the inoor rowing machine is shown in Fig.2. The muscle contraction accounts or the non-linear orcelength property, an orce-velocity property,, o the l muscle an scales the muscle activation, act, by maximum isometric muscle orce, F, in orer to obtain the absolute Max muscle orce. The active joint moment or each muscle is then obtain rom the prouct o moment arm an muscle orce (Fig /t ct Musclectivation /t /t Fl ForceLengthRelation Fv ForceVelocityRelation Prouct -C- Maximum Isometric Force Prouct (u Momentrm Muscle Force Prouct2 v ctive Joint Moment The passive muscle properties are ivie into two components: passive elastics, M, an passive viscous joint moments, M vis, j o these moments. Fig.4 Muscle contraction moel ela j. The total joint moment is the combination Fig.2. Inoor Rowing xercise Moel 2.2 Physiological base Muscle Moel. The physiological base muscle moel or inoor rowing exercise was constructe base on the work by Riener an Fuhr (998. The non-linear moel escribes the major properties o muscle an segmental ynamics o human uring FS-assiste inoor rowing exercise. The muscle moel also accounts or the impairment o the patient (paraplegic to relect the real patient behaviors or inoor rowing exercise. The passive joint moments are given as: M ela, M ela, = exp( ϕ.9ϕ ( exp( ϕ 2.97 M ela, = exp( ϕ.494ϕ.25ϕ + exp( ϕ +. exp(.56.2ϕ +.254ϕ +.3ϕ (2 = exp( 2.8.6ϕ.95ϕ (3 exp( ϕ +.349ϕ 5.24 M ϕ (4 vis,j = k j j

3 The moel o each o the muscle group evelope in this work epens on the speciic parameters o the muscle an inepenent parameters o the muscle erive by Riener an Fuhr (998. The non-linear muscle moel evelope is then incorporate into the humanoi moel escribe earlier as a complete moel o paraplegic or inoor rowing exercise. 3. IMPLMNTTION OF CONTROL STRTGIS The total joint moment generate by the muscle moel to rive the rowing sequence epens on stimulate pulse with as the requency is ixe to 33z. speciic control strategy is require to regulate the stimulate pulse with in orer to obtain smooth rowing manoeuvre. In this stuy, our uzzy logic controllers are esigne to control knee extensor an lexor or both legs to perorm smooth rowing manoeuvres. The rowing sequence is ivie into 4 phases. These are Main xtension phase where quariceps muscle is activate to rive the rowing backwar, Resistance xtension phase where amstrings muscle is activate to slow own the rowing backwar manoeuvre, Main Flexion where hamstrings muscle is activate or recovery phase an Resistance Flexion phase to slow own the backwar rowing manoeuvre by activating the quariceps muscle. 3. Design o Fuzzy Logic Controller. There are 3 inputs selecte or the controller. These are the error (ierence between actual knee trajectory an reerence knee trajectory, change o error an selection o rowing phase. The error an change o error are measure rom the Visual Nastran inoor rowing exercise simulation moel as the system outputs. The selection o rowing phase is use as the thir input as to control the selection o muscle to be activate. The output is the stimulate pulse with. Five Gaussian (bell-shape type membership unctions are use or each input, rror an Change o rror. Two membership unctions or rowing phase input an ive membership unctions or output are use. Tables an 2 show the uzzy rules or stimulate pulse with or quariceps muscle when the rowing phase is (xt an (Flex respectively. Tables 3 an 4 show the uzzy rules or stimulate pulse with or hamstrings muscle when the rowing phase is (xt an (Flex respectively. Table Fuzzy rules or Main xtension NB PB PB PB PS PS NS PB PB PS PS Z Z PB PS PS Z Z PS PS PS Z Z Z PB PS Z Z Z Z Table 2 Fuzzy rules or Resistance xtension NB Z Z Z PS PS NS Z Z PS PS PB Z Z PS PS PB PB PS PS PS PB PB PB PB PS PB PB PB PB Table 3 Fuzzy rules or Main Flexion NB Z Z PS PS PB NS Z PS PS PB PB Z PS PS PB PB PB PS PS PB PB PB PB PB PB PB PB PB PB Table 4 Fuzzy rules or Resistance Flexion NB PS PS PS PS Z NS PS PS PS Z Z Z PS PS Z Z Z PS PS Z Z Z Z PB Z Z Z Z Z The rules are typically ire as: I rror is NB, an Change o rror is NB an Selection is xt then the Pulse With is PB. I rror is PB, an Change o rror is NS an Selection is Flex then the Pulse With is PS. 4. SIMULTION RSULTS The control strategy was implemente in Matlab/Simulink with incorporation o inoor rowing exercise moel in Visual Nastran to illustrate the eectiveness o the control metho or FS-assiste inoor rowing exercise. The control objective is to regulate the level o stimulate pulse with or muscle stimulation to perorm smooth rowing manoeuvre by ollowing the reerence trajectory. The reerence knee an elbow trajectory or rowing sequence with upper boy eort is shown in Fig. 5. Fig.6 shows the result o knee trajectory ater several attempts o parameter tuning. It is note that the FLC approach worke very well or the FS-assiste inoor rowing exercise. The knee trajectory ollowe the reerence closely.

4 ngle [egree] 5 5 nee an lbow Reerence Trajectory nee lbow Fig.9 shows the stimulate pulse with generate rom uzzy logic controller output. The quariceps was stimulate or short perio o time to rive the backwar rowing manoeuvre (main extension phase but the hamstrings muscle was stimulate twice an over a longer time to perorm the resistance rive phase an main lexion phase. ngle [egree] Fig.5. Reerence nee an lbow trajectories 5 5 Reerence an ctual nee Trajectory Reerence ctual Fig.6. Reerence an actual knee trajectories Fig.7 shows the error between the reerence trajectory an actual knee trajectory. The error is consiere small or a complex physiological base muscle moel. The maximum error was about 6.3% (7. Fig.8 shows the knee torque generate rom the stimulate muscle extensor an lexor. The amounts o torque generate are in the range o -45.5Nm to 25Nm (negative values inicate the knee extensor, which are acceptable or paraplegics. rror [egree] Torque [Nm] 2 - rror (knee trajectory Fig.7. rror o knee trajectory Torque Generate -6 Fig.8. Torque generate Stimulation [usec] Stimulate Pulse With Qua ams Fig.9. Stimulate pulse with 5. CONCLUSION uzzy logic controller has been successully implemente to regulate the level o stimulation pulse with use to stimulate the knee extensor an lexor muscle or FSassiste inoor rowing exercise. Base on the control strategy evelope, a smooth rowing manoeuvre has been achieve. physiological base artiicially activate muscle moel generates aequate amounts o torque to rive the knee extensor an lexor through out the rowing manoeuvre. It is note that the track, where the seat slies, is positione horizontally (normally incline. This leas to higher stimulation o hamstrings muscle (knee lexor compare to quariceps muscle (knee extensor ue to hamstrings as a weaker muscle group. Future work will investigate ierent egrees o inclination o track to achieve optimal stimulate pulse with or smooth rowing manoeuvre with consieration o muscle atigue an upper boy eort. RFRNCS nrews, B.J. an G.D. Wheeler (995, Functional an therapeutic beneits o electrical stimulation ater spinal cor injury. Current Opinion in Neurology, vol. 8, pp Davooi, R., B.J. nrews an G.D. Wheeler (2, Moiie concept 2 TM rowing machine with manual FS controller or total boy exercise in paraplegia. Proceeings o International FS Society, pg Davooi, R., B.J. nrews an G.D. Wheeler (22a, Manual an utomatic Control o FS-ssiste Inoor Rowing xercise. Joint MBS-BMS Conerence, ouston, Texas, US, pg Davooi, R., B.J. nrews, G.D. Wheeler an R. Leerer (22b, Development o an inoor rowing machine with manual FS controller or total boy exercise in paraplegia." I Trans. Neural Syst. Rehabil. ng., vol, no. 3, pg

5 Davooi, R., B.J. nrews an G.D. Wheeler (22c, utomatic Finite State Control o FS-ssiste Inoor Rowing xercise ater Spinal Cor Injury. Journal o International Neuromoulation society, vol. 5, no. 4, pg Massou, R. (27, Intelligent control techniques or springassiste FS-cycling, PhD Thesis, Department o utomatic Control an System ngineering, University o Sheiel, Unite ingom. Raymon, J., G.M. Davis, M. Climstein, an J.R. Sutton (999, Cariorespiratory responses to arm cranking an electrical stimulation leg cycling in people with paraplegia, Me. Sci. Sports xerc., vol. 3, pp Riener, R., J. Quintern, an G. Schmit (996, Biomechanical moel o the human knee evaluate by neuromuscular stimulation, J. Biomech., vol. 29, no. 9, pp Riener, R. an J. Quintern (997, physiologically base moel o muscle activation veriie by electrical stimulation. Bioelectrochemistry an Bioenergetics, vol. 43, pg Riener, R. an T. Fuhr (998, Patient-riven control o FS-supporte staning-up: simulation stuy, I Trans. Rehab. ng., vol. 6, no. 2, pp Riener, R. (999, Moel-base evelopment o neuroprostheses or paraplegic patients. Philosophical Transactions o the Royal Society (Lonon B Biological Science, vol. 354, pg Riener, R., M. Boll,. Pavan, M. Ferrarin, R. Spaone, an C. Frigo (999, Control experiments with a neuroprosthesis or staning-up an sitting-own, Proc. Biomechatronics Workshop, nschee, The Netherlans, pp Riener, R., M. Ferrarin,. Pavan an C.. Frigo (2, Patient-Driven Control o FS-Supporte Staning Up an Sitting Down: xperimental Results. I Transactions on rehabilitation engineering, vol. 8, no. 4. Wheeler, G.D., B. nrews, R. Leerer, R. Davooi,. Natho, C. Weiss, J. Jeon, Y. Bhambhani, an R.D. Steawar (22, Functional electric stimulationassiste rowing: Increasing cariovascular itness through unctional electric stimulation rowing training in persons with spinal cor injury. rch Phys Me Rehabil, vol. 83, no. 8, pg Winter, D.. (99, Biomechanics an motor control o human movement, 2 n eition, Wiley Interscience, New York.