2. Energy Optimization of Transverse Flux
Motor for Use in Bionic Ankle
By: Sebastian Roubert
Research Advisor: Cameron Taylor, Ph.D. Candidate
Faculty Advisor: Dr. Hugh Herr
3. Previous Bionic Ankle Design
• PowerFoot BiOM emulates natural stride without
increasing metabolic cost
• Limited to 1,500 to 2,000 steps on a charge
• Motor complex overheats after 600 consecutive
steps and causes high acoustic noise
• hiFigure 1: Previous generation ankle with
labels. Image credit: Cameron Taylor
4. Characterizing Motor Needs
Figure 2: Torque-speed profile of human
step. Image credit: Cameron Taylor
Figure 3: Torque and velocity plotted separately
versus time. Image credit: Cameron Taylor
5. Next Bionic Ankle Design
• Utilizes transverse flux motor with novel motor design
• Motor dimensions determined which optimize
efficiency
• Latest optimization package reduced power loss from
27 W to 9 W
Figure 4: Next generation ankle with
labels. Image credit: Cameron Taylor
6. • Current creates alternating north and
south poles in flower petal rotor poles
• Permanent magnets create alternating
north and south poles in yellow and red
pieces of metal
Transverse Flux Motor
Figure 5: CAD rendering of single phase novel
transverse flux motor topology.
7. Modeling and Simulating Motor Operation
• Model made in SolidWorks, computer
aided drafting software
• Model analyzed for efficiency through
simulation in JMAG, magnetic
modeling software
Figure 6: JMAG rendering magnetic flux vectors
through single phase pi-section. Image credit:
Cameron Taylor
8. Figure 7: Brief Flowchart of previous optimization package.
Modeling and Simulating Motor Operation
9.
10. Figure 8: Appended Optimization Package Flowchart.
Modeling and Simulating Motor Operation
11. • Previous optimization accounted for laminations through
approximations
• New, more robust model accounts for laminations
Improvements to Model
Figure 9: Previous model.
Image credit: Cameron Taylor
Figure 10: New model accounting for
laminations.
Image credit: Sebastian Roubert
12. • Provides thorough example of optimization
based design
• Can be adapted to other magnetic modeling
software
• Beginning of modeling prosthetic joints to
meet specific needs
Future Work and Applications
Figure 11:Three-phase Transverse Flux Motor in
SolidWorks. Image Credit: Sebastian Roubert
Imagine mousetrap inside carbon fiber
1: maxon brushless DC motor, commerically available but overheats after around 600 steps and high noise
2: timing belt, contributes to 70% of acoustic noise
3: ball screw which pushes open or pulls close the torsion spring (4)
4: torsion spring, imagine mousetrap
5: all centered around ankle joint
Notice the battery at top
Current motor: Maxon brushless DC motor
1: motor on top of ball screw
2: battery behind ankle
3: motor control electronics
Novel meaning new, how do we pick parameters
Before picking dimension values, we must be able to reliably model and simulate the motor and its operation
