Modular Fuzzy Logic Controller for Motion Control of Two-Wheeled Wheelchair

Most of the wheelchair users are paraplegics, who are not able to move on their own due to permanent injury in their lower extremities. These wheelchairs are four-wheeled and have certain limitations due to design and control mechanism. For example, the wheelchairs cannot move to a higher level, lift the front wheel and stay in an upright position. As a result, wheelchair users cannot reach certain heights to pick and place things on the shelves, and cupboards, etc. without any assistant and also cannot have eye-to-eye conversation with normal people effectively. On the other hand, a two-wheeled wheelchair has a unique characteristic that may help disabled and elderly people who use the wheelchair as the main means of transport and can also use the wheelchair for these added advantages. Now the idea is to transform the standard four-wheeled wheelchair into a two-wheeled upright wheelchair to facilitate such manuoverability. The front wheels (casters) can be lifted up and stabilized as an inverted pendulum, thus increasing the level of height achievable while in the upright position. Similarly, when this upright position is no longer needed it may be transformed back into its normal four-wheeled position. The schematic diagram of the twowheeled wheelchair is shown in Figure 1. The transformation will result in a highly nonlinear and complex system. Since a human has quite significant mass sitting on the wheelchair, the two-wheeled wheelchair can be modeled with double links that mimic double inverted pendulum scenario that need a clever control strategy.