The Robot

The Table Mount is the bottom, stationary link of the robot that fastens to an external rigid surface. It contains a motor-pulley system that rotates the base link. This motor-pulley system is made up of a Pololu 37D 100:1 gearmotor and a 3:1 timing belt pulley system. The motor is mounted to a movable motor plate that can be fastened to the aluminum motor table. This is done to generate tension in the timing belt. Both the 36- tooth pulley and the 12-tooth pulley are XL series belt compatible and will be 3d printed. The 12-tooth pulley will be mounted to the motor’s 6mm D-bore output shaft via a D-bore motor hub. The 36-tooth pulley is mounted between the base link and the table mount. The Pololu 37D gearmotor will rotate the 12-tooth pulley, which will rotate the 36-tooth pulley and the base link. The base link will be directly bolted to the table mount’s base shaft. This aluminum shaft will rest on the inner diameter of both base bearings, while the outer diameter of both bearings will remain stationary with the table mount as they will be press-fit into place. This will allow for the free rotation of the base link, as the only points of contact are through the bearings. At the bottom of the base shaft, an AMT102-V 64cpr quadrature encoder is fastened such that the inner input drive rotates with the base shaft while the rest of the encoder remains stationary with the table mount.

The base link acts as the first rotational link (z-rotation) of the robot. It is mounted to the table mount via 4 ¼” steel bolts. The base link houses the motor-pulley system that drives link 1. This is made up of a 36-tooth pulley, a 12-tooth pulley, and a 100:1 Pololu 37D gearmotor. The Pololu 37D gearmotor is mounted directly to the frame of the base link via slot holes. These slot holes allow the motor to be vertically adjusted, allowing the timing belt to gain tension, eliminating belt slop. The 36-tooth and 12-tooth pulleys’ connection form a 3:1 gear ratio from the motor to link 1 using a ¼” XL timing belt. The 12-tooth pulley is connected to the Pololu 37D gearmotor’s D-bore 6mm output shaft using a 6mm D-bore aluminum hub. The 36-tooth pulley is connected to rotational shaft 1 for the second rotation using a 6mm aluminum hub. This rotational shaft passes through bearings press-fit on the base link and is connected to 6mm aluminum hubs that are fastened to link 1. This allows for link 1 to rotate freely about the rotational shaft with the 36-tooth pulley. The rotational shaft also passes through an AMT102-V 64cpr quadrature encoder such that the inner input drive rotates with the rotational shaft while the rest of the encoder remains stationary with the base link.

Link 1 acts as the second rotational link (y-rotation) of the robot. Its rotational movement is driven by a motor-pulley system in the base link. Additionally, Link 1 houses a motor-pulley system used for driving link 2. It is made up of a of a 36-tooth pulley, a 12-tooth pulley, and a 70:1 Pololu 37D gearmotor. The combination of the 36- tooth pulley and 12-tooth pulley gives a gear ratio of 3:1 from the motor to the rotation of link 2. The Pololu 37D gearmotor is mounted directly to the motor slide, which is mounted to the chassis of link 1 with slot holes. This allows for the Pololu 37D gearmotor to be vertically adjusted such that tension in the ¼” XL timing belt can be attained. The 12-tooth pulley is mounted to the Pololu 37D gearmotor’s D-bore 6mm output shaft using a 6mm D-bore aluminum hub. The 36-tooth pulley is mounted to rotational shaft 2 using a 6mm aluminum hub. Rotational shaft 2 connects to link 2 via 2 6mm D-bore aluminum hubs, allowing link 2 to rotate with rotational shaft 2. Both ends of rotational shaft 2 rest in bearings press-fit into link 1 such that link 2 can rotate freely. Rotational shaft 2 also passes through an AMT102-V 64cpr quadrature encoder such that the inner input drive rotates with the rotational shaft while the rest of the encoder remains stationary with link 1.

Link 2 acts as the third rotational link (y-rotation) of the robot. Its rotational movement is driven by a motor-pulley system in link 1. Link 2 also houses a 70:1 Pololu 37D gearmotor that drives the rotation of link 3 directly. The Pololu 37D gearmotor’s 6mm D-bore output shaft fastens to a 6mm D-bore aluminum hub, which fastens to link 3. This is done so that link 3 can freely rotate with the output shaft of the Pololu 37D gearmotor. The Pololu 37D gearmotor’s 6mm D-bore output shaft also passes through an AMT102-V 64cpr quadrature encoder such that the inner input drive rotates with the output shaft while the rest of the encoder remains stationary with link 2. The curved shape of link 2 allows for space to aid in assembling its components. The offset in the zdirection creates a larger range of joint limits as it can fold parallel with link 1 without clashing.

Link 3 acts as the fourth rotational link (x-rotation) of the robot. It is driven directly by the motor in link 2. Additionally, link 3 houses a motor-pulley system used for driving link 4. It is made up of two 12-tooth pulleys, and a 156:1 Pololu 20D gearmotor. The Pololu 20D gearmotor is mounted directly to the motor slide, which is mounted to the chassis of link 3 with slot holes. This allows for the Pololu 20D gearmotor to be adjusted such that tension in the ¼” XL timing belt can be attained. The 12-tooth pulley connected to the motor drive is mounted to the Pololu 20D gearmotor’s D-bore 4mm output shaft using a 4mm D-bore aluminum hub. The 12-tooth pulley on link 4 is built as a solid part with link 4 such that link 4 will rotate with the pulley. A 4mm rotational shaft is conjoined with link 4 via a 4mm aluminum hub and rotates on link 3 via press fit bearings. This rotational shaft also passes through an AMT102-V 64cpr quadrature encoder such that the inner input drive rotates with the rotational shaft while the rest of the encoder remains stationary with link 3.

Link 4 acts as the fifth rotational link (y-rotation) of the robot. Its rotational movement is driven by a motor-pulley system in link 3. Link 3 also houses a 156:1 Pololu 20D gearmotor that drives the rotation the last rotation of the robot directly with a 4mm output shaft.