Session: ASME Undergraduate Student Design Expo

Paper Number: 176158

Laboratory on Experimental Verification of Four-Bar and Crank-Slider Linkages in a Senior-Level Design and Modeling Course 

Analyses of four-bar and crank-slider linkages are covered in various fundamental courses in mechanical engineering. Topics typically tackled are kinematics, forces, stresses, input torque, etc. Students are also exposed to different analysis software and in many cases, use tools like MATLAB to calculate relevant parameters for all positions of the linkage. In certain courses, students may also be constructing table-top prototypes of linkages to demonstrate their understanding of four-bar linkages used in different applications. 

In the above approach, there is one drawback, which is the lack of experimental verification of linkage prototypes with design criteria. A review of capstone project reports involving linkages carried out at Worcester Polytechnic Institute showed that in over half of the projects, there is insufficient, or no data collected on the prototype that can be used to verify that it meets the design criteria. In many cases, the linkages are in moving condition and this qualitative condition is being considered as satisfactory verification, which is not sufficient from an industry standpoint. There are many reasons for this, such as lack of bandwidth in courses to accommodate laboratory exercises, lack of time in capstone projects to accommodate experimental verification, and lack of resources necessary to provide adequate exposure to students among other reasons. 

This poster highlights a laboratory exercise that was developed and implemented into a senior level modeling course in mechanical engineering at WPI. The exercise involved a four-bar linkage with revolute joints and a crank-slider linkage. The linkages were fitted with inertial measurement units and encoders to measure angle and angular velocities of links at their centers of mass and at the input respectively. Two types of sensors were used, wired and wireless. Students were provided with detailed information on the installation and calibration of sensors, collection of data and activities necessary to compare sensor data with theoretical calculations. As part of the laboratory exercise in the course, students were required to obtain the kinematics of the linkage either using MATLAB or a related software. Following this, students collected measurements from various sensors, after necessary calibration, and then would follow the instruction guide to deduce comparisons between sensor data and theoretical calculations, essentially obtaining the root mean squared error. 

There were multiple objectives of this laboratory exercise. The first one was to showcase the importance of experimental verification and the process of doing that. The second objective was to demonstrate the need for using multiple sensors. The third was to emphasize the repeatability and reproducibility aspects since during the course of the laboratory exercises, the sensors had varied performance, which was not anticipated during the prior verification and validation tests. 

Students were guided in the process of collecting data and processing data by the teaching team. Over 150 students participated in this activity during multiple instances of the course. The poster will provide detailed implementation information along with future work recommendations that can allow implementation of this laboratory in other universities.

Presenting Author: Samuel Gervasi Worcester Polytechnic Institute

Presenting Author Biography: BS/MS Mechanical Engineering Student at Worcester Polytechnic Institute

Authors:

Samuel Gervasi Worcester Polytechnic Institute
Caleb Cotoia Worcester Polytechnic Institute
Pradeep Radhakrishnan Worcester Polytechnic Institute
Cam Tu Lee Worcester Polytechnic Institute