Energy Demonstration Bicycle

Students: Esteban Delgadillo, Nick Fitzpatrick, Jason Franklin

Sponsor: The University of Texas at Austin

Date: Spring 2010

Requirements:
The two highest priorities for the redesign are to appropriately simulate inclines depending on the child's age and realistically simulate acceleration from rest. A third priority for our team is to revisit the interactive portion of the energy bike. During the ride, the energy the user burns, the power produced, the speed of motion, and the distanced traveled are presented. These properties of the bike ride are approximated to reflect realistic outcomes. The DAQ (Data Acquisition) card used is constrained to an output voltage of ±5V. As a result, there can only be three solid state relays powered at one time. Also, we found that at maximum conditions, the power resistors must dissipate 340 Watts. Thus, power resistors must be able to dissipate at least this 340 W if used alone. Adding minor components to the circuit system was rather inexpensive, so cost was not a major constraint.

Problem:
The Energy Demonstration Bicycle simulates a realistic bike ride by applying appropriate torque to the pedals suitable for a given age group, as well as applying an incremental change in torque to resemble the force resulting from acceleration.

Solution:
The final circuit design is a parallel circuit with resistances of 4, 8, 16, 33 Ω on the branches. The new configuration allows us to divide power among multiple circuit loops to reduce the dissipation for each resistor. There are now fourteen resistance options that accommodate three age groups and that can be incrementally varied to simulate the force resulting from acceleration. We implemented an open-loop control model comprising a set of logical instructions to simulate the appropriate dynamic equation responses, step-function behavior, and the inertial response on the pedals resembling a real bike. We refined the velocity signal by using a 2nd-order discrete differentiator LabVIEW VI. Also, we added an age group selection interface that allows the child to enter his/her age, and LabVIEW will then set the appropriate torque to apply to the pedals.

Images related to the project:

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