Omni-Directional Industrial Robot

Industry is the one side of the Indian economy which has seen the maximum amount of mechanization, simultaneously creating a base for international trading ties at its very core. And the kind of technology today needs to be constantly maintained and upgraded not only due to wear and tear but also with respect to the modernization of the tools that can be effective to stay competitive in the global marketplace.

Contrary to popular belief, machines cannot replace men in most construction related businesses; it can only help in faster work completion and building a safe working environment. However, keeping in mind the increasing space constraints, a space effective approach is a welcome solution. For this, Saurabh Ambre and his peers, who have been pursuing their Bachelor's degree in Mechanical Engineering from Rajiv Gandhi Institute of Technology, Mumbai have created an initiative based on Mechatronics (a combination of mechanical, electronic and computer engineering) called the Omnibot.

What is the Omnibot?
As the name suggests, the Omnibot is an acronym for the Omni-directional vehicle with a robotic arm. It can travel in eight directions without changing its reference plane using special wheels called the Mecanum wheels. It gets its name the Swedish engineer Bengt Ilon, who crafted the wheel design in 1973 for the Swedish company Mecanum AB and filed for a patent in the US in 1975.

Saurabh Ambre, the lead for the project, tells us "This project utilizes the Mecanum wheel design. It is a wheel with a series of rollers attached to its circumference. These rollers have an axis of rotation at 45 degrees to the plane of the wheel. Due to Mecanum wheels, the robot can move diagonally at 45 degrees, which is its unique and a useful motion. The robot can rotate 360 degrees on its own axis. Mecanum wheels are useful to move objects without any effort in limited spaces as it does not require a turning radius. Besides moving forward and backward like conventional wheels, they allow sideways movement without changing the reference plane by spinning wheels on the front and rear axles in opposite directions.

”Using four Mecanum wheels provides omni directional movement for a vehicle without needing a conventional steering system. Slipping is a common problem in the Mecanum wheel as it has only one roller with a single point of ground contact at any one time. Due to the dynamics of the Mecanum wheel, it can create force vectors in both the x and y-direction while only being driven in the y-direction. Positioning four Mecanum wheels, one at each corner of the chassis (two mirrored pairs) allows net forces to be formed in the x, y and rotational."

Understanding the Fabrication Design

The Omnibot consists of four Mecanum wheels on the base. The circuitry is nested under the specially hand-crafted chassis and body. The chassis has a unique shape, but the wheels are mounted in a square pattern to get the omni directional drive. A robotic arm is installed at the front side of the robot, which resembles a crane. The fabrication was conduction at Ambre Mechanical Works (AMW). The crane and the wheels are controlled with the help of a micro controller.

"The Mecanum wheel consists of six rollers with same diameter and are custom fabricated to fit the wheel size. The rollers can be made by an engineering plastic called Delrin or by wood. Each wheel has two metal plates and six petals on each plate, therefore six rollers fit into each of the wheels. There should be at least six rollers for each wheel and you can up the number to 8, 12 or even higher. The metal plate is first twisted and then bent to get the 45-degree angle. Each roller is mounted in between two petals of the wheel plate, forming one wheel. The angle between the rollers' axis and central wheel axis could have any value but in the case of conventional Swedish wheel, it is 45 degrees. The angled peripheral rollers translate a portion of the force in the rotational direction of the wheel to a force normal to the wheel direction. Depending on each individual wheel direction and speed, the resulting combination of all these forces produces a total force vector in any desired direction, thus allowing the platform to move freely in the direction, resulting in force vector without changing of the wheels themselves."
Controlling the Bot
At the core of the entire logic of this Microbotic code, lies a microcontroller. Mounted on the bot itself are the motion sensors and the power modules, which are all connected to the microcontroller. The microcontroller coordinates the flow of information and power on the robot. All other electronic system components must interface with the microcontroller. It not only contains of the robot's program, but also processes all signals received from both transmitter and onboard sensor systems. It also manages power allocation on board the robot, and directly controls the motors. The microcontroller is programmed using the C programming language. The transmitter device enables users to control the system.

Commands are entered through the joysticks and buttons on the RF Transmitter, and sent through FM radio waves to the RF Receiver module mounted on the robot. In addition to providing the control link, the transmitter can be used to alter robot control options, such as drive configuration and joystick trims and scaling.

The Robotic Arm
An integral part of the design is a robotic arm installed on the robot. The robotic arm is a multifunctional controller. It has a claw to grab objects and has an arm for to translate motion to go up and down. It doesn’t have an extra mobile base because of the wheels; it gets its mobility from the robot itself. The arm is controlled by a multi-motor controller of the robot. The control is intended to avoid discontinuous motor operation problems. The system receives information from a host machine. Using this information, the controller adjusts the speed of each motor for a continuous movement of the arm. In order to allow a clear explanation, we have restricted the model to two motors only. Despite this simplification, the robot arm controller constitutes quite a complex system.

The robot arm controller is a complex system composed of two communicating modules – an electronic part, the controller, and a mechanical part, the two motors. Because of the nature of the behavior performed by these two modules, different languages are needed.

The electronic part performs a control function and is easier to be described using an extended based language. The mechanical part is described using a continuous model. This system is clearly a heterogeneous system."

About the Creators
The team comprises of Saurabh Ambre, Kalpesh Damle, Amol Pande, Shantanu Mendhekar, Gaurav Rele, and Ajay Patil. The Omnibot has been fabricated at the Ambre Mechanical Works (AMW). Saurabh led the team that created the bot. He has been a member of the The Engineering Society for Advancing Mobility Land Sea Air and Space, and is also gaining proficiency in software applications like AutoCAD, and Pro Engineer.

He believes the project is a practical solution to the already clogged up construction areas. The bot is a prototype and can be worked upon to a robotic arm; it can be replaced with a fork lift to further enhance operational usage and safety norms.

He believes that while the project can be used for commercial usage, it will incur high cost of maintenance (like a forklift, for example), but it can do wonders in industrial usage.

Published Date: Aug 30, 2010 04:03 pm | Updated Date: Aug 30, 2010 04:03 pm