A seat structure with an adjustable sense of sitting comprises a cover and a base plate, wherein an adjusting cavity is defined by the base plate and the cover; at least two soft inner layers different in hardness and breathability are arranged in the adjusting cavity, and the soft inner layers are at least two of a sponge cushion, a 3D mesh cushion and an air fiber cushion; and a cover body is provided with a zipper structure, which can be slidably unzipped to form an opening for adjusting the soft inner layers. The soft inner layers can be taken out via the opening, and users can place multiple soft inner layers in the adjusting cavity in different sequences as required to adjust the hardness and breathability of the seat structure to obtain suitable hardness and breathability so as to improve sitting comfort.

An adjustment device for a seat, which is designed as an extension of a seat plane of the seat. The adjustment device has a length-adjustable adjustment mechanism and at least one elastic tension element. The adjustment mechanism has a central winding roller, multiple sliding rollers, at least one front end part, and at least one rear end part. Each end part is connected to at least one sliding roller. A first end of the at least one tension element is fastened to the central winding roller. The at least one tension element, starting from the central winding roller, touches the sliding rollers. A second end of the at least one tension element is fastened to a fastening element of a supporting body of the seat plane.

A chair includes a plurality of legs, a seat, at least one seat extension member movably connected to the seat, a back support connected to the seat via a frame, the back support having at least one cavity, at least one back support extension member movably received in the at least one cavity, an arm support, and a connector extending between a first seat extension member from among the at least one seat extension member and the arm support, the connector connecting the first seat extension with the arm support. A method of using the chair includes moving the at least one seat extension member away from the seat to widen an area of the chair used for sitting, and/or moving the at least one back support extension member away from the back support to widen an area of the chair used for supporting a user's back.

A seat apparatus having a simulated force feedback and a method for simulating a force sensation of driving are provided. The seat apparatus includes a seating unit, a rotary platform, and a realistic seat pallet. The seating unit includes a seat pan. The rotary platform includes a chassis and a rotary motive module. The seat pan is disposed on the chassis along a rotation axis in an inclinable manner. The rotary motive module can control the seat pan to have a forward or rearward inclined angle. The realistic seat pallet is disposed on the seat pan, and includes a movable contact cushion and a pallet motive module. Through the pallet motive module, the movable contact cushion is slidable relative to the seat pan. The pallet motive module can control the movable contact cushion to have left and right displacements, front and rear displacements, angular displacements, or yaw rotations.