Research On Crossing Redundant Control System For Intelligent Wheelchair Bed

As the trend of population ageing in China seems to be faster and the number of physically disabled people increases rapidly due to all kinds of diseases and traffic accidents,the medical care problem for the elderly and the lower limb disabled poses a huge burden on family and society.This paper proposes a new kind of multifunctional indoor service robot for the elderly and the disabled to relieve this problem,which is composed of four modules: mobile platform,deformation platform,bed base platform and tablet devices.The mobile platform is drived by four independent Mecanum wheels to achieve omnidirectional movements.The deformation platform is able to adjust joint gestures with electric linear actuators.The bed base platform can transform into multifunction nursing-bed when docked with mobile platform,as a result the problem of limb transfer can be averted.An architecture of upper and lower communication using Socket communication interface based on TCP/IP protocol is developed in this paper.The slave computer is able to communicate with tablet devices,Arduino Wido microcontroller through Socket interface and communicate with Arduino Mega microcontroller through RS232 interface with multithreading technology.The control terminal is composed of a remote tablet and a vehicle tablet.To establish a crossing redundancy control system,mutexes are used to keep thread synchronization and an additional discriminant procedure is adopted for control switch.Besides,a set of control softwares and interface are developed based on WinForm.The developed intelligent wheelchair bed system has the functions of motion control,manual or automated wheelchair deformation and obstacle detection.Furthermore,an autonomous returning and docking algorithm based on multi-sensor information fusion is developed to cope with the docking problem of wheelchair unit.Ultrasonic sensors are taken into consideration for positioning in Y direction.In X direction,infrared coding based on NEC protocol is applied for area division to serve as assistant orientation.Basing on artificial landmark matching method,mutation distance on junction surface of bed base is detected for accurate positioning so that return path is simplified and local autonomous docking of wheelchair unit can be achieved.Furthermore,a slip compensation algorithm is proposed to reduce slip impacts on omnidirectional motion precision and enhance local autonomous docking effects.