Four Wheeled Robotic Scanner Introduction

Non-destructive testing (NDT) encompasses a disparate range of techniques which are used to detect internal and surface defects such as cracks, voids, porosity, inclusions and corrosion and play a vital role in many industries to ensure the quality and safety of materials, products and structures. Major users of NDT are the automotive, aerospace, oil and gas, petrochemicals, power generation and offshore industries and while much testing is conducted manually, several NDT techniques may be automated and recent years have seen growing interest in the development of robotic systems. The use of NDT robots generally reflects difficulties or safety issues surrounding access to the component or structure under test. Some examples include liquid storage tanks, pipe-work and pipelines, ships' hulls, offshore structures and the insides of turbines. For these types of applications, wheeled, climbing or crawling robot has been developed.

Rapid inspection of large areas has been an on-going challenge to the NDE community in these days. Field inspection using manual scanning is labour intensive, time consuming and subjected to human error. Effective field inspection requires a portable, user friendly system that can rapidly scan large areas of complex structures. In recent years, various portable inspection systems have emerged including scanners that are placed at selected locations and sequentially repositioned to fully cover the desired areas. As the technology evolves, crawlers would be developed to operate automatically and search for flaws on pipe line and storage tanks without a human interference. Since the introduction of microprocessors, various types of portable scanners were developed using such NDE methods as visual, eddy currents, ultrasonics, shearography, radiography and thermography. While most scanners have been dedicated to a single inspection method, there is an overall trend to combine the capability of more than one inspection method.

To overcome this problem of needing multiple scanners for different containers (pipes, tanks etc.), we have designed one robotic scanner which can be used in various positions and scan various containers as well as, tanks and tank floor etc.

We have designed a Four Wheeled Robotic Scanner. This robotic design includes components and each component has been modelled in Solid Work 3D CAD Software and has been assembled completely. Each component is assembled with required constraints which will give suitable degree of freedom according to the application.

A proper design has been made for probe holder to hold different probes used in Non Destructive Techniques (NDT). Probes are different for varied NDT techniques. Some examples for probes are conventional ultrasonic probes, phased array probes, EMAT probes, Eddy current probes etc. The probe dimensions depend on the scanning method. For example, there is no use of any medium for impedance matching in EMAT and Eddy current testing. However, a couplant (water or gel, which is used in ultrasonic medical field) is needed for conventional ultrasonic and phased array NDTs. Hence a proper design is required for probe holder to fulfil this functionality when these probes have to be used.

A powerful magnetic base cover has been developed in house which will help this robot to stick on to ferrous material of the tank shell.

Details of the Design Components Internal Components

Part 1: Motor

Motor is the first component modelled in 3D CAD software and it is considered as the reference to assemble other components. Motor is the prime part in the whole robot which gives the power for operating the whole robot. This part is featured in figure 1.

Part 2: Coupling Casing

Coupling Casing is the second component after the Motor, through which the motor drive is available in the Gearbox. Coupling Casing is attached to both Motor and Gearbox and its main function is to provide a casing for the coupling which connects the motor shaft and gearbox shaft. This part is featured in figure 2.

Part 3: Gear Box

Gearbox is the most vital component which converts the motor drives rotational axis by 90° and provides torque for the rotation of the Wheel. This is achieved using a Worm wheel and Worm gear. Worm wheel's shaft is a connected to coupling. Worm wheel and Worm gear are mated together such that the drive is transferred normal to the drive provided by the Motor shaft in additional to that Worm gear shaft(Driving wheel shaft) acts as the axle for the Wheel, hence the rotational moment is received at the Wheel axis. This part is featured in figure 3.

Part4: Driving Wheel Shaft

Driving wheel shaft holds the Worm gear at one end and the opposite end is used to attach the robot Wheel. This component is a very critical in whole robot because the main rotational torque acts on this part, as a reason this part is subjected to stress and strain, so that the part is manufactured in a high grade material, to withstand high bending moment. This part is featured in figure 4.

Part 5: Dummy Wheel Robot Joint

Dummy Wheel Robot Joins the part which holds the Dummy Wheel Shaft and it is attached to the Side Frame. This part is designed for the proper holding of the unpowered Wheels. This part is featured in figure 5.

Part 6: Axle To Axle Connector

Axle to Axle Connector connects the Dummy Wheel Robot Joint with the Gearbox.

It provides internal stability to the robot and it also supports the Driving wheel shaft at one end and Dummy Wheel Shaft at the other. This part is featured in figure 6.

Part 7: Dummy Wheel Shaft

Dummy Wheel Shaft acts as a support for the unpowered Wheels. The unpowered Wheels are attached to the Dummy Wheel Shaft at one end and the other end is supported at Axle to Axle Connector. As this part is also subjected to bending moment, this part is also manufactured in high grade material. This part is featured in figure 7.

Part 8: Side Frame

Side Frame is the vital part in the exterior of the robot because all the four axles are connected to this part. All the rest exterior parts are tightened to the Side Frame. The probe holder is attached to one of the Side Frame. This part is featured in figure 8.

Part 9: Side Cover

Side Cover connects two Side Frame and provides a box like structure for robot. This part is featured in figure 9.

Part 10: Bottom Frame

Bottom Frame is fitted with powerful Magnets with the help of magnet pockets, which helps the robot to hold firmly to a ferrous body like tank shell. This part is featured in figure 10.

Part 11: Top Frame

Top Frame is used as an external cover for the robot. This part is featured in figure 11.

Part 12: Magnet Cover

Magnet Cover and Bottom Frame have undercuts, which holds the Magnet in right position and provide necessary sticking capacity to the robot. This part is featured in figure 12.

Part 13: Magnets

Magnets help the robot to stick to a ferrous surface and it also helps it to stand in a prescribed position without moving down due to its self-weight. This part is featured in figure 13.

Part 14: Wheels with Rubber Padding (Wheels)

Wheels are the rolling support for the robot, Wheels which are tightened to Driving wheel shaft avails power from the motor helps in robots to and fro motion. Wheels which are tightened to Dummy wheel shaft just provide the rolling support to the robot. Powered and Unpowered Wheels are connected using Rubber Belts. Powered Wheels on same side drives the Unpowered Wheels on same side with the help of Rubber Belts. Wheels are having groove for accompanying the Rubber Belts in right position. Rubber Padding is provided over the Wheels to get adequate grip while moving over ruff surface. This part is featured in figure 14.

Part 15: Rubber Belts

Rubber Belts are placed over the grooves in the Wheels (which acts as the pulley) helps in transferring drive from powered Wheels to unpowered Wheels. This part is featured in figure 15.

Complete Assembly: "Four Wheeled Robotic Scanner"

The final assembly is shown in figure 16, which includes the proper mating of each part mentioned earlier. This robot also contains one Probe Holder for suitably holding the probe (wedge) in right position for scanning purposes.

Claims

We claim that "Four Wheeled Robotic Scanner" carries probes which can be used for scanning tank floor. Also, it has the capability to climb vertical over tank shell and move circumferentially over it. The main feature of this design is the steering capability of the robot that helps the robot to negotiate sharp turns.

1. We claim that the "Four Wheeled Robotic Scanner" can move over the tank shell in all the possible directions.

2. We claim that the "Four Wheeled Robotic Scanner" can negotiate sharp bends while moving over the tank shell.

3. We claim that the "Four Wheeled Robotic Scanner" will not deviate from its path unless specified to do so.

4. We claim that the "Four Wheeled Robotic Scanner" will not come down to bottom of the tank shell due to its self-weight, while working in a particular height over the tank floor.

5. We claim that the "Four Wheeled Robotic Scanner" is handy, only about 4 kg, but rigid in structure.

6. We claim that the "Four Wheeled Robotic Scanner" is so designed to hold various probes such that it can use various NDT techniques like:

• TOFD (Time Of Flight Diffraction)

• Guided Wave

• Conventional UT (Ultrasonic Testing)

• ECT ( Eddy Current Testing)

• MFL (Magnetic Flux Leakage)

• HOMC (Higher Order Modes Cluster) Guided Wave

• PAUT (Phased Array Ultrasonic Technology)