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Using a humanoid robot for demining land mines
Using a humanoid robot for demining land mines Ahmad Byagowi and Peter Kopacek
Intelligent Handling and Robotics-IHRT, Vienna University of Technology,Vienna, Austria (Tel.: ++4315880131800; e-mail:[email protected]; [email protected]). Abstract: In this paper a humanoid robot for humanitarian demining is described. Humanitarian demining is an important subject in SWIIS. The robot that is demonstrated in this paper is a tall humanoid robot called “Archie” which is a project of the Technical University of Vienna since the year 2004. The robot has the capability to imitate a human gait and could be used for surfing a mined field. Using biped locomotion instead of the traditional wheel based robots has some benefits; in this paper we will try to cover some of them. Keywords: Robots for demining, humanoid robots, human gait imitation, biped locomotion.
1. INTRODUCTION From the systems theoretical and engineering viewpoint SWIIS dealt until now mainly with time continuing systems well known from the field of process automation. Meanwhile in the field of production automation or in terms of systems engineering - time discrete, digital processes - new methods comes up in the last years, probably applicable to the tasks of SWIIS. One of the main ideas of SWIIS in the early eighties was to apply modern methods, developed in systems as well as control engineering for resolution and avoidance of conflicts. More or less conflicts could be seen as a classical stability problem. There are stabilising a de-stabilising parameters. Humanitarian demining is definitely a parameter of the first category. After a conflict – or possibly a war – minefields occupy land, homes, and infrastructure. A lot of organisations worldwide use clearing of minefields and reactivate the land for the displaced local population as an integrating factor in peace discussions to offer native people (e.g. in Kosovo) the possibility to came back to their homes and their lands. As pointed out demining is today a very time consuming, dangerous and expensive task. Automated demining e.g. as presented in this paper by robots, is today and will be in the future a powerful tool to solve these problems and disasters. 1.1 Humanitarian demining and humanoid robots The Institute of “Handling Devices and Robotics – IHRT“ at Vienna University of Technology is working since 5 years in the field of intelligent, low cost mobile robots. Together with the Austrian industry we developed a “toolkit” for mobile robots adapting such robots for various tasks. This tool kit is based on a mobile platform on which various devices (e.g. robot arms, lifts, sensors...) can be attached. With this new concept we have in fact a multipurpose mobile robot for a broad variety of tasks available. These concepts could be also applicable for “Humanitarian Demining” with minor adaptations. Our tool kit for intelligent, mobile robots offers the possibility to develop, in
a very easy and cheap way, demining robots with a broad variety of features (e.g. different mine detecting sensors, different moving mechanisms, various gripping devices...). In a mid or long term perspective it might be possible to develop “Humanitarian Demining Multi Agent Systems – HDMAS” consisting of a number of such robots or agents (Kopacek, 2000). Nowadays robots that are used for humanitarian demining are based on traditional wheel or track locomotion. In this work a different locomotion, based on biped is presented. Using this revolutionary idea brings some advantages such as crossing non-even terrain and difficult crossing paths. According to the mechanical structure of a humanoid robot, the robot will imitate human gait. Using this ability will provide some advantages for the robot. Obviously imitating human like gait will increase the possibility for stimulating land mines which are based for attacking human, which means, in case that the detectors misses finding a land mine, the robot using stepping on the mine can activate the mine. 2. HUMANOID ROBOTS CONTROL CONCEPT The principle of walking in biped robots relies on saving the balance. On this basis the robot calculate the centre of mass in real time using kinematic. Using control methods the robot tries to hold the centre of mass in a region, thus to have the ground projection of it in a safe area which is called support polygon.The task of controlling a humanoid robot is based on dealing with a natural term called gravity, which is applied on all the parts of the robot. In a rigid body, the centre of mass is a fixed point somewhere inside or sometimes near to the object. However, when you add a hinge and connect two rigid objects to each other, the centre of mass will not be in a fixed place anymore and it will change on modifying the situation of the joint between them. This movement will be related to the movement along the joint and the mass of the objects, which are connected to each other using the hinge. For finding the formula that gets the state of the joint and
gives us the position of the centre of mass, forward kinematics should be used. In this paper, we will try to represent a method which is used practically in Archie. To describe the method, first we have to find a base coordinate system (BCS). As it is described before for each rigid body (robot’s links) there is a centre of mass (COM) located on the coordinate system related to the object. However, because we have several links in the robot that are able to be replaced and changed their position comparative to each other; the position of the COM for each one of them could be located in a reference system. Therefore the coordinate system for all the links should be converted to a single reference coordinate system which is called BCS. To convert a coordinate system to another homogeneous transformation is a well-known method which is used in this work.
For a combination of all the displacements shown in figure 2, a transformation matrix which is described in following figure could be used. 𝑇𝑖𝑖−1
𝑐𝑜𝑠𝜃𝑖 𝑠𝑖𝑛𝜃𝑖 𝑐𝑜𝑠𝛼𝑖−1 = 𝑠𝑖𝑛𝜃𝑖 𝑠𝑖𝑛𝛼𝑖−1 0
−𝑠𝑖𝑛𝜃𝑖 𝑐𝑜𝑠𝜃𝑖 𝑐𝑜𝑠𝛼𝑖−1 𝑐𝑜𝑠𝜃𝑖 𝑠𝑖𝑛𝛼𝑖−1 0
0 −𝑠𝑖𝑛𝛼𝑖−1 𝑐𝑜𝑠𝛼𝑖−1 0
𝑎𝑖−1 −𝑠𝑖𝑛𝛼𝑖−1 𝑑𝑖 𝑐𝑜𝑠𝛼𝑖−1 𝑑𝑖 1
Equation 2: transformation matrix. Which the rotation matrix is like figure described below. 𝑐𝑜𝑠𝜃𝑖 𝑅 = 𝑠𝑖𝑛𝜃𝑖 0
−𝑠𝑖𝑛𝜃𝑖 . 𝑐𝑜𝑠𝛼𝑖 𝑐𝑜𝑠𝜃𝑖 . 𝑐𝑜𝑠𝛼𝑖 𝑠𝑖𝑛𝛼𝑖
𝑠𝑖𝑛𝜃𝑖 . 𝑠𝑖𝑛𝛼𝑖 −𝑐𝑜𝑠𝜃𝑖 𝑠𝑖𝑛𝛼𝑖 𝑐𝑜𝑠𝛼𝑖
Equation 3: rotation matrix. 2.2 Base coordinate system
Figure 1: Illustration of two links connected to each other with different coordinate system.
2.1 Homogeneous transformation Homogeneous transformation is a method which uses a transformation matrix for converting the position of a point in a specific coordinate system to another coordinate system. In this method, translation and orientation are possible to be converted between two coordinate systems. Equation 1 shows a homogeneous transformation matrix, which can change the translation and the orientation for a position. ⋯ ⋮ ⋯ ⋮ 𝑃 𝐴 = ⋯ 𝑅𝐵𝐴 ⋯ ⋯ ⋮ … ⋮ 1 0 0 0
⋮ 𝐴 𝑃𝐵(𝑜𝑟𝑔 ) ⋮ 1
Equation 1: homogeneous transformation matrix.
The matrix consists of a rotation matrix that changes the orientation of the location and the translation matrix, which change the offsets. The movement in the joints of the robot can cause changing in orientation as well as the offset. Figure 3 shows the possible movements to be presented in the robot.
Using the homogeneous transformation, the position of the centre of mass for all the joints will be calculated based on a unified coordinate system, which is called based coordinate system (BCS). This coordinate system could be applied in each point of the robot. However, the best place in which it will reduce additional necessary calculations is on the ground, where the robot is standing on and in a point between the two gaits, which is shown in figure 3.
Figure 3: Ground projection of base coordinate system (BCS). The transformation could also be used along the some of the joints and will be a result of the multiplication of all of the transformations used for the joints between two certain points. For example, when it is necessary to find the transformation between link #1 and link #5, a multiplication of all the links between them will provide us the necessary transformation.
𝑇51 = 𝑇21 × 𝑇32 × 𝑇43 × 𝑇54
Equation 4
2.3 Total centre of mass After getting the position of all the centre of mass points for each joint related to the BSC system, the total centre of mass can be calculated for the whole robot. The centre of mass for the robot will be calculated using (Equation 5).
𝐶𝑀𝑡𝑜𝑡𝑎𝑙 = 𝑚
Figure 2: a) attached using a convention. b) Twisting between two links. C) Angles between two links.
1 𝑡𝑜𝑡𝑎𝑙
𝑚𝑖 𝐶𝑀𝑖
Equation 5
Figure 4: a) centre of mass for each link individually b) the total centre of mass for the robot shown with a circuled black spot
Figure 6: Frontal view of lifting sequence for SSP phase During this sequence the support polygon will be limited as it shown in figure 7.
3. WALKING SEQUENCE Walking and a biped system consist of two phases, double support phase (DSP) and single support phase (SSP). In the double support phase both legs of the robot are in touch with the ground. On the other hand, the single support phase is when only one leg of the robot is in touch with the ground and the second one is swinging. Walking will be possible executing this two phases repeatedly, which the robot will move one step using the SSP and stabilize on the DSP phase and for the next movement the SSP will be applied for the second leg. 3.1 Double support phase (DSP) In the Double support phase both legs are touching the ground and the support polygon will consist from the area between the two legs. During this phase the robot will not have any displacement related to his foots. But the robot will have a movement to change the centre of mass from one leg to the second one. This movement will be similar to a shuffle movement.
Figure 7: The support polygon for DSP shown in (a) changes decreases to area where the stand foot touches the ground (c) 3.3 Walking To get the robot walk the DSP and SSP should be executed repeatedly for the left leg and the right leg as shown in figure 11. DSP with left leg in front
Lifting the right leg
Putting the left leg on ground
SSP-left (right leg swing)
SSP-left (right leg swing) Lifting the left leg
Left step
Righ t step
Putting the right leg on ground DSP with right leg in front
Figure 8: walking sequences for left and right leg 4. THE HUMANOID ROBOT ARCHIE Figure 5: Sagittal view of two consecutive DSP phases
Archie is a tall humanoid robot with 150cm high and consists of 30 joints. Figure 9 depicts a view of Archie.
3.2 Single support phase (SSP) In the single support phase only one leg of the robot will be in touch with the ground and the second leg will be lifted up from it, during this phase the support polygon will be limited to the area in which the standing leg is in touch with the ground. To hold the balance during this phase, the centre of mass should be located in the support polygon. In order to do this, the robot tries to put all the weight on the standing leg, as it shown in figure 6. Figure 9: Illustration of Archie
4.1 Joints in Archie The joint in Archie use brushless motors coupled with a harmonic drive, which gives the robot very high performance and efficiency.
Figure 12: Magnetic field emitted and received in the MDS The sensor used in this project is based on pulse inductive (PI) 5.2 Metal recognition Figure 10: Modular joint constructed and used in Archie
Using the PI method the material of the metal could be recognized. Figure 12 shows the different responses with different metals.
5. LANDMINE DETECTION SENSOR The Land mines are almost detectable using a metal detector circuit except some type of them that are called plastic mines. In plastic mines there are also some metal parts which makes them also detectable but with more difficulties. The metal detector sensor (MDS) could be mounted on the bottom of the legs of the humanoid or using an arm and swinging around the robot during walking. Figure 10 shows a leg from Archie.
Figure 13: Graph of different metal responses in MDS Recognizing the type of the metal can improve the result and can also increase the accuracy of the system. For example using this method metal parts are differentiable from land mines. 6. CONCLUSIONS
Figure 11: Illustration of Archie’s leg 5.1 Metal detector sensor (MDS) The simplest form of a metal detector sensor consists of an oscillator producing an alternating current that passes through a coil which produces an alternating magnetic field. If a piece of metal is close to the coil, eddy currents will be induced in the metal, and this produces an alternating magnetic field. If another coil is used to measure the magnetic field in the magnetic field due to the metallic object can be detected.
As pointed out earlier all the existing and planned robots for humanitarian demining are only able to detect the mines. Brutal force methods destroy mines without detection – but with a not reasonable probability. In a next step our robots have to be able to remove the mines from the ground. In this work an innovational idea for using a humanoid robot as deminer is presented. Using a humanoid robot for the deminer task can be very beneficial. Which robot will imitate human like gait and this will give him the ability to pass through muddy and non-even trains that are difficult for normal traditional wheel based locomotion robots. Also the robot will be more accurate in sensing the mine field and will touch minimum areas (only the foot print of gait) in compare with a wheel or track based robot, and this will decrease the possibility of the land mine attacks during detection. This project is a new step in this area and there should be a lot of improvements carried out on this theme, as well as increasing the robustness of the humanoid robot and decreasing the weight and the cost. This is a pioneer project that can create a revolution for the demining and protects humans more than before against land mines.
REFERENCES [1]- Kopacek, P. (1999): Preprints of the IARP Workshop on “Humanitarian Demining”, Harare, November 1999. [2]- Kopacek, P. (2000): SWIIS – An Important Expression of IFAC’s Commitment to Social responsibility, Preprints of the IFAC Workshop on Supplemental Ways for Improving International Stability – SWIIS 2000, 22. – 24. May 2000, Ohrid, Macedonia [3]- Grosvenor, Edwin S. and Wesson, Morgan. Alexander Graham Bell: The Life and Times of the Man Who Invented the Telephone. New York: Harry N. Abrahms, Inc., 1997. ISBN 0-8109-4005-1. [4]- Grad, Paul (17 Dec 2008). "Detecting Land Mines: New Technology". Asian Surveying and Mapping. [5]- Graves M, Smith A, and Batchelor B 1998: Approaches to foreign body detection in foods, Trends in Food Science & Technology 9 21-27 [6]- Everett, H. R. (1995). Sensors for Mobile Robots: Theory and Application. AK Peters. ISBN 1-56881-048-2. [7]- Asada, H. and Slotine, J.-J. E. (1986). Robot Analysis and Control. Wiley. ISBN 0-471-83029-1. [8]- Goswami, Ambarish. Postural Stability of Biped Robots and the Foot-Rotation Indicator (FRI) Point. The International Journal of Robotics Research, Vol. 18, No. 6, 523-533 (1999). [9]- Vukobratović, Miomir and Borovac, Branislav. Zeromoment point Thirty five years of its life. International Journal of Humanoid Robotics, Vol. 1, No. 1, pp. 157-173, 2004.
Intelligent Handling and Robotics-IHRT, Vienna University of Technology,Vienna, Austria (Tel.: ++4315880131800; e-mail:[email protected]; [email protected]). Abstract: In this paper a humanoid robot for humanitarian demining is described. Humanitarian demining is an important subject in SWIIS. The robot that is demonstrated in this paper is a tall humanoid robot called “Archie” which is a project of the Technical University of Vienna since the year 2004. The robot has the capability to imitate a human gait and could be used for surfing a mined field. Using biped locomotion instead of the traditional wheel based robots has some benefits; in this paper we will try to cover some of them. Keywords: Robots for demining, humanoid robots, human gait imitation, biped locomotion.
1. INTRODUCTION From the systems theoretical and engineering viewpoint SWIIS dealt until now mainly with time continuing systems well known from the field of process automation. Meanwhile in the field of production automation or in terms of systems engineering - time discrete, digital processes - new methods comes up in the last years, probably applicable to the tasks of SWIIS. One of the main ideas of SWIIS in the early eighties was to apply modern methods, developed in systems as well as control engineering for resolution and avoidance of conflicts. More or less conflicts could be seen as a classical stability problem. There are stabilising a de-stabilising parameters. Humanitarian demining is definitely a parameter of the first category. After a conflict – or possibly a war – minefields occupy land, homes, and infrastructure. A lot of organisations worldwide use clearing of minefields and reactivate the land for the displaced local population as an integrating factor in peace discussions to offer native people (e.g. in Kosovo) the possibility to came back to their homes and their lands. As pointed out demining is today a very time consuming, dangerous and expensive task. Automated demining e.g. as presented in this paper by robots, is today and will be in the future a powerful tool to solve these problems and disasters. 1.1 Humanitarian demining and humanoid robots The Institute of “Handling Devices and Robotics – IHRT“ at Vienna University of Technology is working since 5 years in the field of intelligent, low cost mobile robots. Together with the Austrian industry we developed a “toolkit” for mobile robots adapting such robots for various tasks. This tool kit is based on a mobile platform on which various devices (e.g. robot arms, lifts, sensors...) can be attached. With this new concept we have in fact a multipurpose mobile robot for a broad variety of tasks available. These concepts could be also applicable for “Humanitarian Demining” with minor adaptations. Our tool kit for intelligent, mobile robots offers the possibility to develop, in
a very easy and cheap way, demining robots with a broad variety of features (e.g. different mine detecting sensors, different moving mechanisms, various gripping devices...). In a mid or long term perspective it might be possible to develop “Humanitarian Demining Multi Agent Systems – HDMAS” consisting of a number of such robots or agents (Kopacek, 2000). Nowadays robots that are used for humanitarian demining are based on traditional wheel or track locomotion. In this work a different locomotion, based on biped is presented. Using this revolutionary idea brings some advantages such as crossing non-even terrain and difficult crossing paths. According to the mechanical structure of a humanoid robot, the robot will imitate human gait. Using this ability will provide some advantages for the robot. Obviously imitating human like gait will increase the possibility for stimulating land mines which are based for attacking human, which means, in case that the detectors misses finding a land mine, the robot using stepping on the mine can activate the mine. 2. HUMANOID ROBOTS CONTROL CONCEPT The principle of walking in biped robots relies on saving the balance. On this basis the robot calculate the centre of mass in real time using kinematic. Using control methods the robot tries to hold the centre of mass in a region, thus to have the ground projection of it in a safe area which is called support polygon.The task of controlling a humanoid robot is based on dealing with a natural term called gravity, which is applied on all the parts of the robot. In a rigid body, the centre of mass is a fixed point somewhere inside or sometimes near to the object. However, when you add a hinge and connect two rigid objects to each other, the centre of mass will not be in a fixed place anymore and it will change on modifying the situation of the joint between them. This movement will be related to the movement along the joint and the mass of the objects, which are connected to each other using the hinge. For finding the formula that gets the state of the joint and
gives us the position of the centre of mass, forward kinematics should be used. In this paper, we will try to represent a method which is used practically in Archie. To describe the method, first we have to find a base coordinate system (BCS). As it is described before for each rigid body (robot’s links) there is a centre of mass (COM) located on the coordinate system related to the object. However, because we have several links in the robot that are able to be replaced and changed their position comparative to each other; the position of the COM for each one of them could be located in a reference system. Therefore the coordinate system for all the links should be converted to a single reference coordinate system which is called BCS. To convert a coordinate system to another homogeneous transformation is a well-known method which is used in this work.
For a combination of all the displacements shown in figure 2, a transformation matrix which is described in following figure could be used. 𝑇𝑖𝑖−1
𝑐𝑜𝑠𝜃𝑖 𝑠𝑖𝑛𝜃𝑖 𝑐𝑜𝑠𝛼𝑖−1 = 𝑠𝑖𝑛𝜃𝑖 𝑠𝑖𝑛𝛼𝑖−1 0
−𝑠𝑖𝑛𝜃𝑖 𝑐𝑜𝑠𝜃𝑖 𝑐𝑜𝑠𝛼𝑖−1 𝑐𝑜𝑠𝜃𝑖 𝑠𝑖𝑛𝛼𝑖−1 0
0 −𝑠𝑖𝑛𝛼𝑖−1 𝑐𝑜𝑠𝛼𝑖−1 0
𝑎𝑖−1 −𝑠𝑖𝑛𝛼𝑖−1 𝑑𝑖 𝑐𝑜𝑠𝛼𝑖−1 𝑑𝑖 1
Equation 2: transformation matrix. Which the rotation matrix is like figure described below. 𝑐𝑜𝑠𝜃𝑖 𝑅 = 𝑠𝑖𝑛𝜃𝑖 0
−𝑠𝑖𝑛𝜃𝑖 . 𝑐𝑜𝑠𝛼𝑖 𝑐𝑜𝑠𝜃𝑖 . 𝑐𝑜𝑠𝛼𝑖 𝑠𝑖𝑛𝛼𝑖
𝑠𝑖𝑛𝜃𝑖 . 𝑠𝑖𝑛𝛼𝑖 −𝑐𝑜𝑠𝜃𝑖 𝑠𝑖𝑛𝛼𝑖 𝑐𝑜𝑠𝛼𝑖
Equation 3: rotation matrix. 2.2 Base coordinate system
Figure 1: Illustration of two links connected to each other with different coordinate system.
2.1 Homogeneous transformation Homogeneous transformation is a method which uses a transformation matrix for converting the position of a point in a specific coordinate system to another coordinate system. In this method, translation and orientation are possible to be converted between two coordinate systems. Equation 1 shows a homogeneous transformation matrix, which can change the translation and the orientation for a position. ⋯ ⋮ ⋯ ⋮ 𝑃 𝐴 = ⋯ 𝑅𝐵𝐴 ⋯ ⋯ ⋮ … ⋮ 1 0 0 0
⋮ 𝐴 𝑃𝐵(𝑜𝑟𝑔 ) ⋮ 1
Equation 1: homogeneous transformation matrix.
The matrix consists of a rotation matrix that changes the orientation of the location and the translation matrix, which change the offsets. The movement in the joints of the robot can cause changing in orientation as well as the offset. Figure 3 shows the possible movements to be presented in the robot.
Using the homogeneous transformation, the position of the centre of mass for all the joints will be calculated based on a unified coordinate system, which is called based coordinate system (BCS). This coordinate system could be applied in each point of the robot. However, the best place in which it will reduce additional necessary calculations is on the ground, where the robot is standing on and in a point between the two gaits, which is shown in figure 3.
Figure 3: Ground projection of base coordinate system (BCS). The transformation could also be used along the some of the joints and will be a result of the multiplication of all of the transformations used for the joints between two certain points. For example, when it is necessary to find the transformation between link #1 and link #5, a multiplication of all the links between them will provide us the necessary transformation.
𝑇51 = 𝑇21 × 𝑇32 × 𝑇43 × 𝑇54
Equation 4
2.3 Total centre of mass After getting the position of all the centre of mass points for each joint related to the BSC system, the total centre of mass can be calculated for the whole robot. The centre of mass for the robot will be calculated using (Equation 5).
𝐶𝑀𝑡𝑜𝑡𝑎𝑙 = 𝑚
Figure 2: a) attached using a convention. b) Twisting between two links. C) Angles between two links.
1 𝑡𝑜𝑡𝑎𝑙
𝑚𝑖 𝐶𝑀𝑖
Equation 5
Figure 4: a) centre of mass for each link individually b) the total centre of mass for the robot shown with a circuled black spot
Figure 6: Frontal view of lifting sequence for SSP phase During this sequence the support polygon will be limited as it shown in figure 7.
3. WALKING SEQUENCE Walking and a biped system consist of two phases, double support phase (DSP) and single support phase (SSP). In the double support phase both legs of the robot are in touch with the ground. On the other hand, the single support phase is when only one leg of the robot is in touch with the ground and the second one is swinging. Walking will be possible executing this two phases repeatedly, which the robot will move one step using the SSP and stabilize on the DSP phase and for the next movement the SSP will be applied for the second leg. 3.1 Double support phase (DSP) In the Double support phase both legs are touching the ground and the support polygon will consist from the area between the two legs. During this phase the robot will not have any displacement related to his foots. But the robot will have a movement to change the centre of mass from one leg to the second one. This movement will be similar to a shuffle movement.
Figure 7: The support polygon for DSP shown in (a) changes decreases to area where the stand foot touches the ground (c) 3.3 Walking To get the robot walk the DSP and SSP should be executed repeatedly for the left leg and the right leg as shown in figure 11. DSP with left leg in front
Lifting the right leg
Putting the left leg on ground
SSP-left (right leg swing)
SSP-left (right leg swing) Lifting the left leg
Left step
Righ t step
Putting the right leg on ground DSP with right leg in front
Figure 8: walking sequences for left and right leg 4. THE HUMANOID ROBOT ARCHIE Figure 5: Sagittal view of two consecutive DSP phases
Archie is a tall humanoid robot with 150cm high and consists of 30 joints. Figure 9 depicts a view of Archie.
3.2 Single support phase (SSP) In the single support phase only one leg of the robot will be in touch with the ground and the second leg will be lifted up from it, during this phase the support polygon will be limited to the area in which the standing leg is in touch with the ground. To hold the balance during this phase, the centre of mass should be located in the support polygon. In order to do this, the robot tries to put all the weight on the standing leg, as it shown in figure 6. Figure 9: Illustration of Archie
4.1 Joints in Archie The joint in Archie use brushless motors coupled with a harmonic drive, which gives the robot very high performance and efficiency.
Figure 12: Magnetic field emitted and received in the MDS The sensor used in this project is based on pulse inductive (PI) 5.2 Metal recognition Figure 10: Modular joint constructed and used in Archie
Using the PI method the material of the metal could be recognized. Figure 12 shows the different responses with different metals.
5. LANDMINE DETECTION SENSOR The Land mines are almost detectable using a metal detector circuit except some type of them that are called plastic mines. In plastic mines there are also some metal parts which makes them also detectable but with more difficulties. The metal detector sensor (MDS) could be mounted on the bottom of the legs of the humanoid or using an arm and swinging around the robot during walking. Figure 10 shows a leg from Archie.
Figure 13: Graph of different metal responses in MDS Recognizing the type of the metal can improve the result and can also increase the accuracy of the system. For example using this method metal parts are differentiable from land mines. 6. CONCLUSIONS
Figure 11: Illustration of Archie’s leg 5.1 Metal detector sensor (MDS) The simplest form of a metal detector sensor consists of an oscillator producing an alternating current that passes through a coil which produces an alternating magnetic field. If a piece of metal is close to the coil, eddy currents will be induced in the metal, and this produces an alternating magnetic field. If another coil is used to measure the magnetic field in the magnetic field due to the metallic object can be detected.
As pointed out earlier all the existing and planned robots for humanitarian demining are only able to detect the mines. Brutal force methods destroy mines without detection – but with a not reasonable probability. In a next step our robots have to be able to remove the mines from the ground. In this work an innovational idea for using a humanoid robot as deminer is presented. Using a humanoid robot for the deminer task can be very beneficial. Which robot will imitate human like gait and this will give him the ability to pass through muddy and non-even trains that are difficult for normal traditional wheel based locomotion robots. Also the robot will be more accurate in sensing the mine field and will touch minimum areas (only the foot print of gait) in compare with a wheel or track based robot, and this will decrease the possibility of the land mine attacks during detection. This project is a new step in this area and there should be a lot of improvements carried out on this theme, as well as increasing the robustness of the humanoid robot and decreasing the weight and the cost. This is a pioneer project that can create a revolution for the demining and protects humans more than before against land mines.
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