Since the booming AIGC technology has been introduced into the design field to improve efficiency, the work aims to improve the application quality of AIGC in complex product industrial design combined with big data technology and double diamond model. An AIGC collaborative "1+2 diamond" industrial design process model was proposed to improve the process efficiency and solution quality of AIGC collaborative industrial design through three divergences and three convergences. Firstly, the demand issues were diverged with the assistance of ChatGPT and big data crawling by Python, and the design goals were converged with the help of high-frequency word analysis by Python, competitive product analysis and expert review. Secondly, creative ideas were diverged through fuzzy drawing by Midjourney's stop parameter, and the design direction was converged through a questionnaire survey of project personnel. Finally, DALL.E, Stable Diffusion and Midjourney were employed in conjunction to generate divergent design details. The final solution was determined through focus group convergence and the modeling rendering was completed. A comprehensive, professional and accurate demand analysis was conducted on the airway clearance for long-term bedridden elderly people. The assistive device design solution was recognized by design and engineering professionals in terms of user-friendliness, aesthetic appeal, technical feasibility and functional usability. The "1+2 diamond" design process which integrates AIGC, big data and conventional industrial design methodologies, can efficaciously enhance the quality of AIGC collaborative industrial design by manually controlling AIGC's reference content, processing AIGC's generated content and conducting periodic expert evaluation, which offers insights into the standardized AIGC collaborative industrial design process.