Team Vision for System-Level Design Phase
Following our last design review we have begun to meet with members of the Tigerbot V team and are in the process of understanding their designs. We have decided to use their work as a stepping stone rather than redo the concept selection and research they have already completed. We have updated some of their designs and intend to have a full design for our prototype by the next review. In addition, we will begin testing the walking code once we have located all of the parts necessary for this testing.
Revised Engineering Requirements
During phase 2 we had a meeting with Dr. Sahin which helped us narrow down the requirements of the project, and thus we felt it necessary to revise the engineering requirements.
Snapshot of engineering requirements:
Though we intend on using much of 15201's work as a stepping stone, we wanted to do our own functional decomposition and single out the parts that are most important to 16201.
16201 Benchmarking Data
15201 Benchmarking Data
ContextAs a team, we decided that a major focal point of our project would be to re-design the ankle+foot portion of the tigerbot to make it more human-like. In this section we will show the concepts we have come up with, and explain their advantages/disadvantages.
Sketches page 1 - details below image
Ankle Design 1: This design is a "pulled apart" design based on last year's group. It uses servos and gearboxes to drive the 2 degree of freedom ankle
Ankle Design 2: This design utilizes linear actuators to provide the forces needed to move the ankle. This design has been revised to only use two actuators; one on the front and one on the side.
Leg Design 1: This is virtually the same as last year's design, except the plates are used again for increased stability.
Sketches page 2 - details below image
Leg Design 2: Here, an actuator is used to drive the knee movement. Plates are used for the structure to increase stability from last year's design.
Sketches page 3 - details below image
Top: This is an idea for the connection of actuators to the foot plate, along with the leg frame.
Middle: This is a drawing showing a trussed solid frame idea I came up with to reduce weight while retaining structural strength and stability.
Bottom: An example of how to implement the trussed frame into a leg design.
Sketches page 4 - details below image
Top: An example of how to implement truss frame with hip motors.
Bottom: Example of how actuators could be used at the hip joint to improve precision and give wider range of motion than normal motors.
15201's concept selection is shown below. Not included here are the harmonic gearboxes, which provide the same qualities as the cycloidal gearboxes, but are much smaller. Cycloidal gearboxes proved to be too large and heavy, and so are not being used in the final design.
Unified vs Single Pack
- LM317 regulator chosen
- Very common, easily replaced
- Can take max input voltage of 40VDC
- Servos will be run ~48+ VDC
- Unified PSU is not feasible
- Teknic ClearPath-MCPV (Precision Position Control)
- Absolute Positioning
- Pulse Burst Positioning
- Paired with select gearboxes will allow required torque
- McMaster-Carr DC Gearmotors
- Don’t require a gearbox
- Can be set parallel to the joints or perpendicular to the joints.
- For use on shoulder and elbow joints.
- Either Carbon Fiber Composites or Kevlar Epoxy Cycloidal Gear
- Cycloidal Gear
- Carbon Fiber is light but prone to break from shock.
- Kevlar resists shocks
- Zero Backlash
- Great for balancing the hip
- Reduces energy use.
Feasibility: Prototyping, Analysis, Simulation
15201 Feasibility Document
Actuator Feasibility calculations
We conducted a feasibility analysis to determine if actuators can provide enough force and speed to mimic human motion considering the weight of the full-scale Tigerbot.(full document not pictured. See download link.)
Risk Assessment Snapshot
Design Review Materials
Plans for next phase
- Begin design process
- Acquire all 15201 materials
- Achieve Final understanding of 15201 materials
- Begin ordering parts