Experimental Evaluation of Mechanical Design Parameters in Multi-Stage Compliant Intakes

Abstract

Autonomous robots are increasingly used to handle objects with varying positions and orientations in applications such as cleanup, recycling, and warehouse automation. Intakes with compliant (flexible) rollers must lift objects from uneven surfaces, transfer them without stalling, and prevent jamming. Although compliant intake mechanisms have been studied in robotic collection and harvesting systems, relatively few experimental studies have isolated how individual mechanical design parameters influence performance in multi-stage compliant intakes. To experimentally evaluate the influence of mechanical design parameters on intake performance, a high-speed, multi-stage compliant intake for collecting tennis balls from turf was developed and tested through four wheel designs and three intake iterations. The resulting 350 mm-wide intake was designed to collect an entire row of regulation tennis balls simultaneously. Testing showed that wheel material stiffness, rather than axle fit, determined torque transmission reliability in flexible thermoplastic polyurethane (TPU) wheels. Adding textured cloth tape improved ball grip, but tightening the wheel bore and adding spacers did not eliminate shaft slipping. A rigid polylactic acid core with a cross-shaped interlock resolved this issue. Subsequent testing identified singulator jamming and transfer dead zones caused by insufficient roller compression. Increasing ball compression from 8 mm to 10 mm improved traction but did not eliminate the dead zones. These findings informed a third-generation design using continuous closed-cell polyethylene foam rollers, expected to eliminate inter-wheel gaps while removing 18 printed components and approximately 50 manufacturing hours. Overall, these results demonstrate that material stiffness, roller compression, and transfer geometry have a greater impact on intake reliability than dimensional fit alone, providing design guidance for future compliant intake systems