C I R C L E
Overview
Circle is an open-source parallel manipulator robot that is designed to stabilize objects such as cameras and other critical payloads.
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The circle can also be interfaced with other robots. For example, integrating the Circle module with a serial manipulator to combine the dexterity and working volume of a robotic arm with the rigidity and stabilization features of a parallel manipulator.
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Link to GitHub repository:
Project Updates
Robot Inverse Kinematics
To develop the robot inverse kinematic equations, standard link lengths and other kinematic parameters were chosen. The kinematic equations required for open loop implementation have been described in the document attached below.
Robot Controller
The robot controller uses the STM32F103C8T6 microcontroller. For the purpose of fine motor control, the DRV8825 is used and can be micro-stepped to 1/64. For the purpose of pose estimation and feedback, the MPU9250 9 axis IMU Module is used over an I2C line. Homing operations are performed with the help of normally open(NO) limit switches. The controller is powered using a 5V SMPS module currently and will later be upgraded to a Li-ion Battery source. The electronic schematic for the controller has been described in detail in the document attached below.
Proof of Concept Development
A proof of concept was developed as part of stage 1 of the project to verify the kinematic equations and algorithms governing the motion of the robot. An open-loop control was implemented in order to test the robot concept. The videos below show the various tests that were conducted.
Linear Motion Test
Combination of Rotary and Linear Motion Test
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Design Upgrades (October 2020)
The following upgrades have been done to the platform:
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1. The mechanical design has been upgraded in order to handle higher payloads as well as reduce compliance in parts during manipulation.
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2. The microcontroller has been upgraded from an ATmega328p (Arduino Uno) to an STM32 F103C8T6 which has a smaller form factor and a faster processor.
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3. Stepper motors and drivers with micro-stepping capabilities have been incorporated into the design to facilitate finer motion control.
4. MPU 9250 a 9 axis MEMS-based inertial tracking device has been used to track the orientation of the end effector in real time and provide feedback to the on board closed-loop control system.
Upgraded Robotic Platform
