Proposal for

Robotic Landmine Detector

Team 9:

Nicholas Young, Ryan Singh, Chengkai Hsiao, Keron Henry 

Advisor:

Rajeev Bansal

Robotic Landmine Detector

Executive Summary

This project will consist of a robot that will search a sandy beach-like environment for landmines. The robot will be autonomously navigated till the presence of metal is detected, and then the robot will be switched over to the user. The user will then mark where the landmine is with a few drops of paint, and then continue the search.

Statement of Need

Landmines are an efficient weapon used by approximately 48 countries through out the world and produced by over 100 companies. These weapons have a life span that is far beyond most of the conflicts they are deployed in. Therefore, these weapons will typically end up killing just as many civilians after the conflict than actual soldiers. It is estimated that 70 people are killed or injured by landmines everyday throughout the world. Anyone who falls victim to a landmine will only have a 50% chance of surviving and even if an individual does survive, they will suffer great personal injury.

The detection and removal of landmines posses a formidable challenge to the world, and there exists a need for a device that can find mines before they claim another victim. Due to the widespread usage of landmines, there are many differing environments that a detection device would have to be able to work in. Also, due the many differing variations in mines, a device would have to be able to recognize a wide range of materials that are used to produce landmines.

Specifications

The landmine detector will operate in a sandy environment that is characterized as being relatively flat. The robot must have an internal motor to facilitate motion coupled with either wheels or a track. It is also necessary for the robot to have an electrical system that will stop the robot when a mine is found and allow a human to navigate the robot.

Project Description

Methods

The landmine detector consists of five major subsections including: batteries, motors, metal detector, user interface, and central controls.

Block Diagram

Motors

The motors will be used to physically move our robot around by driving two tracks. Therefore, we have decided to use two motors where each motor would power one track. When we were exploring options in regards to what kind of motor will be used, we thought that either DC motors or stepper motors would make the best choices. This was due to the fact that the robot will be carrying all of its power on board in the form of batteries. Therefore, it would be illogical to choose a motor that does not use DC, if an AC motor were chosen, then the motor would require an extra circuit to change from DC to AC.

Knowing that DC motors and stepper motors would provide the best options, we then looked at each type of motors characteristics of operation. Obviously, with in the general title of DC motors there exists a wide variety of subsets but the chief types consist of permanent magnets and field coil. In general, DC motors are characterized by possessing high torque from standstill and are easily controlled by varying the applied voltage. A DC motor with a permanent magnet seems like a better choice due to the fact that it is lighter than a DC motor with a field coil. The stepper motor also provides many advantages, such as its precise speed control, and a large amount of torque. The only disadvantage is that it requires a switching circuit. With these ideas in mind, we came to the conclusion that a DC motor with a permanent magnet would provide the best results. This was due to the fact that it does not require any other circuits to be built, thus keeping our design simpler in nature.

Batteries

There exist a wide variety of batteries to choose from. To narrow our search, we wanted a battery that would be rechargeable. This choice was an obvious one due to the fact that they are more economic than nonrechargable batteries in the long run. The two most common rechargeable batteries fall into two categories, either Nickel-cadmium (NiCd) or Nickel-metal Hydride (NiMH). In comparing these two, the NiMH has a lower weight than the NiCd when the amount of Power is used to make the comparison.

Paint

The paint portion of our design will be used as the means to mark the spot of the mine. To do this, we will use a plastic line connected at one end to a small container of paint and at the other end placed in the middle of the metal detectors coil. When metal is detected, and the user knows about where the metal is, he or she will flip a switch in order to allow paint to drip out on to the sand. Paint will drip out because we will allow air to flow into the paint container and gravity will then be able to draw the paint out.

Metal Detector

The first step in our process of choosing a metal detector came from deciding whether to buy a fully functional metal detector or constructing one from scratch or a kit. Buying a fully functional device had the obvious advantage or being a preassembled and not requiring any assembly. It would require modifications so that its output to the user could then be sent to our control system. The main disadvantage that is caused by this pertains to the fact that most of these commercially produced units have an analog output in the form of a meter. In order to make use of this output, we would then have to open up the unit and figure out the inner workings of the metal detector. Also, it would be hard to figure out the electronics of the unit due to the fact that most user guides are written without the intent of an individual modifying the metal detector. Buying a kit would also have many advantages and disadvantages. The advantages are that the kit would have more detailed explanations of the inner workings of the electronics thus facilitating modifications. We could then easily send the signal indicating the presence of metal to the control system in the form we desired. The disadvantages would range from the fact that we would have to build the unit and there would also be a fair amount of experimentation necessary for our desired operation characteristics. Building one from scratch is one option that we feel does not offer significant advantages. It would require too much experimentation. We based this on past experience obtained in ECE261, where we built a metal detector. Through this experience, we all encountered significant problems, and there were also constraints in our design that would make its uses in this particular project negligible. The constraints were due to the fact that the metal detector used the physical characteristics of inductors where the presence of metal changes its properties. This would only allow a small area to be surveyed.

With these things in mind, we decided that the kit was the best option. It would provide the best results for our project and would also allow for many modifications in our design process.

User Controls

The user controls will have to be built so that an operator can override the internal controls. This would occur when metal is detected thus switching the motors off and control over to the user. The options for the user controls are as follows: to either take preexisting electronics from a radio controlled car, or other comparable device and modifying them, or build one from scratch. The advantages of modifying a preexisting unit pertains to the fact that an RC device already has all of the circuitry needed to steer the robot with only slight modifications needed. The disadvantages are derived from the limited range that some of these devices have. The modifications to the unit would include the ability to send a signal to the robot that would allow air to flow into the paint container when the specific location of the mine is decided upon. Other options include building a RC unit from scratch or a kit. The disadvantages range from the design and experimentation necessary to achieve the desired results. The advantages are that we would be able to have our user control device do exactly what we want.

As a group we came up with the following conclusion, that the best way to approach this problem would be to use the electronics of a preexisting device. We would only have to add another component to allow for the paint unit to mark the desired location. Also, there may be a need to increase the range of the device to allow the user to be a safe distance from the area of interest. This could be done by increasing the size of the antenna and/or amplifying the current.

Central Controls

The central control will have to be designed by our team. Due to the fact that our system is unique in that it has never been built before, there do not exist a commercial unit for sale. To do this without getting into too much detail, we will make use of a microcontroller. The microcontroller will be the PIC16F87x. This was the choice that we made due to the fact that we all have some experience with it from ECE266. The central control unit will have several functions. It will have to control the voltage to the DC motors so that the robot can be navigated. It will also have to keep track of the general location of the unit so that it can know when to turn. The PIC will also need to take the information from the metal detector and relay it to the user.

Conclusion

The basic project requires the assembly of a device to help facilitate the removal of landmines in a sandy environment. The device will be autonomous till the point were the mine is located where the user will then take over and mark the location. The area searched will be 25 meters squared in approximately 1 hour or less.