# Development and Validation of a System for Game Control Based on a Force Plate
## 1 Introduction  
A force plate is a mechatronic device that measures the ground reaction force caused by movements of the human body, such as walking, running, or jumping. Research on human walking, balance, and postural stability is often related to an assessment of the center of mass (CoM) of the human body, as well as measuring its center of pressure (CoP) [1; 2; 3]. The human body's CoP is defined as the point in the transverse plane of the human body that represents the total force acting on a person's feet, and it can be quantified directly by using a force plate [4; 5].  
A force plate is most commonly used in the context of biomedicine for the purpose of analyzing human walking, balance, and postural stability. In [6; 7], the authors analyzed postural stability and human balance by measuring shifts in the human body's CoP while standing still. This was accomplished by using developed low-cost portable force plates. The authors in [8] used two force plates to measure the distribution of load on the left and right leg, with the goal of assessing leg length discrepancy. In [9], the authors used the Nintendo Wii Balance Board for the analysis of human walking, which is a low-cost and portable force plate for game control.  
Portable force plates for game control are often used for patient rehabilitation [10]. For that purpose, workout and rehabilitation video games are made, which are controlled via force plates [11], or rather defined patient movements. The leading commercial force plate for game control today is the Nintendo Wii Fit Balance Board [12; 13]. The Nintendo Wii Fit Balance Board is intended for sports and fitness games, which means that it isnot necessarily compatible with other kinds of games. Additionally, the Nintendo Wii Fit Balance Board is not compatible with other operating systems, such as Windows and Linux, and it is not intended for online games. The system for game control based on a force plate described in this paper is compatible with online games, as well as the Windows and Linux operating systems, which are its main advantages compared with the commercial Nintendo Wii Fit Balance Board.  
By altering the position of the human body's CoM, the loads on the left and right leg are changed, meaning that there is a shift in the human body's CoP in the transverse plane. Measuring the position of the human body's CoP using a force plate can be used to control games [5; 14] by simulating keyboard key pressing or mouse cursor movements. A person can use a force plate to generate an acceleration of the CoM along the \(z\) axis (which is perpendicular to the force plate) with a half squat, which allows for the simulation of pressing an additional keyboard key or mouse click.  
The authors of this paper suggest a new system for game control based on a force plate which is adapted to players and allows control of games by changing the position of the player's CoP and accelerating his or her CoM along the \(z\) axis. The game control system is a portable, compact, and low-cost device with the option to simulate the UP, DOWN, LEFT, RIGHT, and SPACE keyboard keys or mouse cursor movements and left mouse button clicks. It consists of a force plate used to measure the human body's CoP using four load cells, an electronic board used for measuring and PC communication via USB, and a PC application for data acquisition, system calibration, and game control. Prior to using the system, a system calibration procedure is performed for each player. This adapts the system to each player, thereby ensuring the best game control experience.  
This article is organized in the following way. A short description of the game control system is provided in Section 2. Section 3 showcases a mathematical model of the system. The developed and produced mechatronic game control system based on a force plate is shown in Section 4. The experimental results obtained by using the game control system are described in Section 5. Finally, Section 6 is a brief conclusion.