Swings That Think
"Swings That Think" is a family of devices that provide real-time motion analysis and audio, tactile, or visual feedback to the user engaged in a task that requires coordination of body movements, and possibly some extra body affordance, (e.g., a golf club, tennis racket, fishing pole, or baseball bat). The devices perform three functions: sensing, analyzing, and providing feedback to the user. Each device consists of a collection of "wearable" sensors such as ankle and wrist straps, belts, and hats that sense characteristics of the user's posture and motions as the user engages in various activities. The preferred method of feedback is audio, although feedback may be provided through visual or tactile mechanisms as well.
The batting belt helps softball or baseball players to improve their batting technique. The system analyzes player and bat motions during each swing and generates real-time audio feedback for the player.
The wireless system uses two small computers and FM radio transmitters to send sensor data to the main computer. One of the transmitters is inside the bat. It is connected to a PIC microcontroller that reads and processes information from the bat gyroscope and accelerometer. The transmitter uses the bat as an antenna. The on-board computer in the bat provides the main computer with the bat speed, swing trajectory, and ball impact data. Those parameters are the most valuable information about players performance. The second small computer is inside the belt pack. It sends information about player's body motion using its own transmitter. This part of the system helps to analyze player's batting technique. The main computer (PC) receives and correlates all the sensor information and generates real-time audio feedback. After each swing the system finds possible mistakes in the batting technique and tells the player what to do to bat better.
The main computer analyses relative position and values of extremes of sensor readouts. For example, during a swing the bat's angular velocity [gyroscope value] reaches a peak, which may be followed by a ball impact trough. The difference between peak and trough values generally corresponds to the amount of energy transferred from the bat to the ball.
Old version with wires
The older version of the system used a single Motorola 6811-based computer inside the belt to collect information from all sensors on the body and inside the bat. The bat was connected with a wire to the belt computer. And the belt computer had a wire connection to the main computer and a power supply.
The bat sensors detect angular velocity and acceleration of the bat. The shoulder gyroscope measures body rotation.
The beltpack holds a small computer which performs initial processing of data from the sensors and sends information to the PC.
The foot accelerometer detects when the player makes a step. The belt currently requires a wire link to the PC.
The pitching machine throws a ball.
Inside the batting cage.