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Modeling of Human Quadriceps Muscles and Design of a Magnetorheological Fluid-based Muscle Strengthening Device

Seifi, Mohammad Mahdi | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45742 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farahmand, Farzam; Behzadi Poor, Saeed
  7. Abstract:
  8. The Quadriceps Muscle as one of the major muscles of the human body plays a key role in knee function. Strengthening of this muscle is recommanded to prevent knee pain and even cure some diseases. Many believe that by strengthening the medial part with respect to the lateral part of the quadriceps muscles, patellofemoral pain syndrome can be prevented or treated. In this regard, a muscle strengthening system, based on magneticorheological brake is designed which provides isometric, isotonic and isokinetic exercise of knee joint and also enables the selective muscle strengthening. Beforehand a musculoskeletal model of lower extremity is developed in OpenSim software, capable to estimate force and activity of each component of the quadriceps muscles. Musculoskeletal model consists of six components of quadriceps and pelvis, femur, patella and tibia. Knee joint is modeled as a two degree of freedom joint that can model tibial rotation as well as knee flexion/extension. Output of the model suggests that isokinetic knee extension in high speed with external tibial rotation is the optimal exercise that leads to a higher VMO/VL activity ratio. Experimental measurement of quadriceps EMG activity was performed to evaluate the suggession of the model and the results fully verified the prediction of the model. After finding the optimal exercise to strengthen muscles, the device was designed. The device consists of the body, leg brace, ankle brace, foot brace, torque and speed sensors, gearbox and magnetorheological brake. The structure of device provides possibility of axial rotation of the leg and ankle with respect to femur. Magnetorheological brake as the core of device has the task of producing adjustable resistive torque. Brake includes stator, rotor, coil and magnetorheological fluid. As the current in the coil is changed, fluid viscosity changes in a few milliseconds and thus differeret torques can be produced. According to the requirements of the standard knee exercises, a cylindrical shape brake with a diameter of 108 mm, height of 60 mm, weight of 2.4 kg is designed that with maximum power consumption of 50 Watts, is able to generate maximum braking torque of 60 Newton-meters. For isotonic and isometric exercises, it is necessary to provide a constant torque and for isokinetic exercise, a fixed brake shaft speed should be maintained. Therefore, a control system consisting of three loops is design and simulated so that the torque and speed can be controlled
  9. Keywords:
  10. Musculoskeletal Modeling ; Isokinetic ; Magnetorheological (MR)Fluid ; Electromyography ; Quadriceps Muscles

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