Design and Manufacture of an Adaptive Suspension SystemMichael Gifford (ME), Tanner Landis (ME/AE), Cody Wood (ME)

Advisors: Professor Cagdas Onal (RBE/ME), Siamak Ghorbani-Faal (RBE)

ABSTRACT This project focuses on the design, development, evaluation, and analysis of an adjustable vehicle suspension system. This system is aimed to improve vehicle performance on all terrain conditions from rough to flat surfaces. The proposed design is accomplished through the modification of a double-triangulated four-bar linkage suspension. The modifications allow the upper links of the suspension system to change vertical position on-the-fly, to meet operator preference. The position change alters suspension geometry and therefore the performance characteristics of the vehicle; specifically the anti-squat which impacts vehicle sag and therefore traction. Thus, traction is directly controlled through adjustments to the suspension system. Through video motion analysis of the modified and unmodified prototype vehicle, we determined the effect of the suspension design. Future applications of this design are expected to improve the performance characteristics of vehicles of all sizes ranging from mobile robots to automobiles. In addition to scalability, the advantage of our design is the on-the-fly adaptability. This enables adjustments in suspension performance for the terrain or obstacle being traversed.

DESIGNOur universal suspension system design for our lab scale prototype consisted of four major parts: a slotted bracket, slide bracket, horizontal cross member and electrical rotational servos. These parts were designed and fit to allow our prototype vehicle with a range of anti-squat between 35 and 172%.

• Charts were broken down into subsections to analyze the performance of the vehicle over a number of obstacles and terrains• The performance of the vehicle on various terrains was found to be dependent on the position of the links• The universal system provided immediate and exact vertical position change of the upper links of the suspension through the use of the user interface• Linkages do not bind at maximum wheel articulation, even with additional components added• Plastic material was not ideal for the application due to the high torque of the motor• Prototype motor was not accurately scaled; therefore there was more torque on the system than would be present in a full scale model

CONCLUSIONSIt was determined that the universal system design improved the functionality of the prototype vehicle over numerous terrains and obstacles. Although, one setting would not improve the performance over all terrains, driver experience could be used to determine the best position for any individual obstacle. The “on-the-fly” adaptability of the system provided the operator with a means to make adjustments while traversing the terrain.

FUTURE PLANS• Convert 3D printed prototypes to various materials dependent upon the application• Apply the design to vehicles of all types • Determine an efficient and cost effective design using different actuators that will provide digital readout of link placement and anti-squat effect in comparison to the origin

ACKNOWLEDGEMENTSThe Project Big Bertha team would like to thank the Rapid Prototyping Team and Ming Luo for their help with our project. We would also like to extend a very special thank you to our advisors Professor Cagdas Onal and Siamak Ghorbani-Faal for their continued support throughout this Project.

METHODOLOGY

Slotted BracketSlide Bracket

•Provides a connection point between the upper links and the rotational servos •Designed to fit in the interior of the slotted bracket and provide a secure connection between the links and the slotted bracket•Bracket was designed to rotate to avoid impedance by surrounding surfaces and material

Slide Bracket

Rotational Servo•Used a Futaba S3003 Electric Rotational Servo•Connecting rod translates rotational motion from servo into vertical motion of the upper links

Horizontal Cross Member•Provides a connection point for the slotted bracket to the frame of the vehicle•Designed to fit on top of the existing vehicle frame rails

Cross Member

Rotational Servo

The initial design of the universal system

Purchase of a lab scale prototype that uses a double triangulated 4 link suspension system

Unmodified lab scale prototype

3D printing of componentsand retrofitting to the lab scale prototype

Modified lab scale prototype

RESULTS

Slotted Bracket•Provides a track to guide the links vertical movement•Designed to allow for ±0.15 inches of travel from center•Slot was designed to have the same radius as the rotating link to ensure a smooth travel surface