Welcome to my webpage. I'm a Ph.D. student in Mechanical Engineering at Penn State. My research is in the area of human biomechanics. In my dissertation work, I am developing patient-specific computational models of body segments such as the foot that can be used for simulations and improvement of orthopedic surgeries. These surgeries involve altering the mechanics of the musculoskeletal system, including fusing joints together, shifting portions of bones, and relocating tendon attachment points to change the lines of action of muscle forces. I use tools traditionally important in mechanical engineering, including numerical optimization and finite element analysis, to create these models.
Please check out the links below for my vitae and videos showing some of my work...
FEA #1: rear view and FEA #2: oblique view These two videos are from finite element simulations of the human foot (the heel and ankle area only) during different loading scenarios. The model includes several rigid bones (grey), nonlinear spring ligaments which connect the bones, a deformable hyperelastic heel pad (with colors showing stress levels), and a flat floor. The complex bone geometries are obtained from MRI imaging and 3D reconstruction. Parameters defining the ligaments are estimated using a numerical optimization which seeks to match the simulation results with x-ray measurements of the patient being modeled. Several optimization strategies including bio-inspired and traditional gradient-based methods are being investigated, and parallel computing is being utilized. The resulting model is 'patient-specific' and can be used to predict outcomes of complex orthopaedic surgeries which alter the mechanics of the foot.
Haptics video: This shows a project in which I developed a haptic (force-feedback) system and display. C-code controls the motor torque of the 'robotic arm' I'm holding, such that it feels like I'm physically moving around a rotary mass-spring 'snap-through' system. The state of this virtual mass-spring system is shown on the computer screen in real-time using a Matlab GUI (with the stretching spring shown in blue). Haptics has applications in areas including remotely-controlled robotic surgery.
MRI/subtalar joint project schematic: This drawing shows experimental apparatus used to move the human foot primarily about the subtalar joint, so that measured 3D kinematics can be used to locate a best-fit subtalar joint axis for musculoskeletal modeling purposes. A 3D dyanamic analytical model was used to determine a closed-form solution for optimal force lines-of-action for applying these motions. MRI measurements of foot bone kinematics were used to assess the accuracy of this new method.
Ill-posedness of optimization problem: This animation demonstrates a fundamental source of ill-posedness of a method proposed for modeling the human ankle complex. The method involves using optimization to size and fit a universal joint kinematic model to an individual's measured 3D ankle kinematics. This process is similar to design synthesis of a robotics mechanism. The ill-posedness is rooted in the fact that, for relatively small ranges of motion, very similar kinematics can be obtained from two very different universal joints. For example, in the video, U-joint 1 (which results in the trajectories of the red markers) is oriented differently than U-joint 2 (yellow markers) by 30 degrees in the horizontal plane. This ultimately results in an optimization cost function that is poorly-conditioned in certain ways.