November/December 2011

Case study: Integrator develops automated endurance test system for cargo bikes

By Jody Koplo

A global nonprofit organization that designs and distributes bicycles used for transportation in poor, rural regions approached DMC, a Chicago-based control system integrator, about creating an automated bicycle clutch testing platform. The specialty clutch being tested was designed for use in specially designed bicycles that provide low-cost, sustainable transportation for people and cargo in developing countries.

The bicycles distributed by World Bicycle Relief (www.worldbicyclerelief.org) need to be able to withstand large loads, rough terrain, and inclement weather. Every component that goes into the bicycle must be sturdy, easily maintained without specialized tools or extensive mechanical knowledge, and have minimal failure modes under heavy extended use and harsh operating conditions. These requirements, in turn, necessitated that considerable endurance and life-cycle testing be performed on the customer's newly designed clutches to verify their suitability for the World Bicycle Relief program. 

DMC designed the test system to perform fully automated endurance, fatigue, and life-cycle testing of a new clutch design by simulating real-world bicycle riding.

Special use calls for rigorous testing

The automated endurance test system needed to be able to perform extended tests of a week or more without operator interaction. The system also needed to provide a highly configurable test sequence for the customer to perform virtually any conceivable simulated operation motion profile. World Bicycle Relief wanted interactive real-time data plotting of angular position, velocity, and motor current/torque, with ability to zoom time focus, toggle displayed channels, and configure plot styles. Continuous logging of test data to file at a user-defined data rate was necessary.

Finally, the test system needed to be extensible. Platform development included creation of a LabVIEW driver for Animatics Smart Motor (a servo motor commonly used by the customer for multiple applications), allowing easy re-use of source code in the future for other automated systems.

DMC delivers versatile test system

DMC developed a LabVIEW application to perform automated endurance and life-cycle testing of bicycle clutches. The LabVIEW application controls an Animatics "SmartMotor" servo that is coupled to the clutch. By rotating the clutch through specified angular displacements at specified angular velocities, the system simulates extended operation of the clutch under real-world bicycle riding conditions. 

The system includes a highly versatile test sequence configuration interface. This allows users to string together series of steps (like basic motion commands) to create complex clutch drive profiles that simulate its actual real-world operation. Such motion profiles can then be repeated for any desired number of test cycles. The ability to run long duration endurance tests with one click with no need for operator intervention or supervision has allowed the customer to collect extensive and valuable data with minimal time commitments from engineers or technicians.

Access to markets, healthcare, education

According to World Bicycle Relief, the right kind of bicycle is an ideal low-cost, efficient, and sustainable development tool for the rural poor. A durable cargo bike can increase carrying capacity five-fold over "headloading," the most common form of rural transport, which involves carrying goods on the head. While inexpensive, headloading is inefficient and drives gender inequity. Bicycling is on average three times faster than walking and significantly less costly than motorcycles and cars. World Bicycle Relief estimates more than 1 billion people worldwide lack adequate transportation to markets, clinics, and schools.

DMC delivered the automated endurance test system to the client in record time, with professional and personal pride. Many DMC employees have long been a part of the bicycle community, making this project a good fit for their expertise as well as their personal passions.

ABOUT THE AUTHOR

Jody Koplo (Jody.Koplo@dmcinfo.com) is a senior project engineer at DMC, a CSIA Certified member that provides engineering and custom software development services for manufacturing, testing, and product development organizations worldwide from its Chicago headquarters. More information about the Control System Integrators Association (CSIA) is available at www.controlsys.org.