Abstract:
A mobile robot generally including a first suction module, a second suction module and a hinge assembly pivotably connecting the suction modules together. Each of the suction modules includes a support frame defining a vacuum chamber and a vacuum unit supported on the support frame and communicating with the vacuum chamber. The vacuum unit includes a rotating impeller and an exhaust cowling surrounding the impeller. The impeller has an axis of rotation and is adapted to draw air from the vacuum chamber into the impeller in a direction generally parallel to the impeller axis of rotation and to discharge the drawn air in a direction substantially perpendicular to the impeller axis of rotation. The exhaust cowling is adapted to redirect the discharged air, whereby a thrusting force is applied to the support frame in a direction opposite of the direction of the drawn air from the vacuum chamber.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to mobile robots and more particularly to robots capable of climbing and traversing horizontal, angled and vertical surfaces, including making transitions between the two. 
   It has been known in the art to provide mobile robots with the capability of moving in a two-dimensional plane to perform functions in the areas of national defense, surveillance and counter terrorism missions. Many successful robot platforms have emerged, but many of such mobile robots are limited to movement in a two-dimensional plane without wall-climbing capability. 
   Some robots have been developed with wall climbing capability by using magnetic devices, suction cups, or attraction force generated by a propeller. Applications for these types of climbing robots focused on inspection and maintenance tasks in hazardous environments, primarily in the nuclear, space, and chemical industries. 
   It has been a long-time desire to develop a miniature climbing robot with the ability to climb walls, walk on ceilings and transit between different surfaces, thus transforming the present two-dimensional world of mobile rovers into a new three-dimensional universe. For example, U.S. Pat. No. 5,839,532 to Yoshiji et al. discloses a vacuum wall walking apparatus having a frame and a plurality of leg mechanisms with suction cups. The frame is composed of a flexible member, making the frame bendable to conform to the profile of a curved surface when the device is used with a wall having such a curved surface. 
   Other robots developed for traversing nonplanar surfaces use articulated structure. For example, U.S. Pat. No. 5,551,525 to Pack et al. discloses a climber robot having front and rear legs joined together by a pivoting knee joint and having pivoting ankle joints at their distal ends. Pneumatic muscle pairs attached to each leg allow the robot to transition from the horizontal to the vertical plane. 
   U.S. Pat. No. 6,619,922 to Illingworth et al. discloses a vortex attractor for planar and non-planar surfaces using a so-called “tornado in the cup” technology. However this prior art has limited payload and has difficulty climbing from a wall to a ceiling or around a corner. 
   Accordingly, it would be desirable to improve upon the prior art by developing new concepts of modularity and mobility for a climbing robot capable of moving between nonplanar surfaces. It would be further desirable to overcome the limitations of prior art robots in terms of robot capability, modularity, control performance, and intelligence to perform various defense, security, and inspection missions. 
   SUMMARY OF THE INVENTION 
   The present invention is a mobile robot generally including a first suction module, a second suction module and a hinge assembly pivotably connecting the suction modules together. (However, it is conceivable that additional suction modules can be employed.) Each of the suction modules includes a support frame defining a vacuum chamber and a vacuum unit supported on the support frame and communicating with the vacuum chamber. The vacuum unit includes a rotating impeller and an exhaust cowling surrounding the impeller. The impeller has an axis of rotation and is adapted to draw air from the vacuum chamber into the impeller in a direction generally parallel to the impeller axis of rotation. The impeller is further adapted to discharge the drawn air from the impeller in a direction substantially perpendicular to the impeller axis of rotation. The exhaust cowling is adapted to redirect the discharged air from the impeller in a direction substantially parallel to the impeller axis of rotation out of the vacuum unit, whereby a thrusting force is applied to the support frame in a direction opposite of the direction of the drawn air from the vacuum chamber. The hinge assembly facilitates nonplanar orientation of the first suction module with respect to the second suction module. 
   In a preferred embodiment, the hinge assembly includes a hinge element fixed to one of the suction modules, a bracket element fixed to the other of the suction modules and coupled to the hinge element about a pivot point and a motor disposed at the pivot point for pivoting the hinge element with respect to the bracket element about the pivot point. In this regard, the support frames of the suction modules are preferably triangular in shape for reducing the torque at the hinge assembly. With this arrangement, the first suction module can be pivoted with respect to the second suction module through an angular range of between +90° and −90°. Other shaped modules, such as circular, rectangular, oval and polygonal, may also be utilized. 
   The vacuum unit exhaust cowling of the suction module preferably includes bowl shaped inner and outer cowlings. Each of the inner and outer cowlings has a bottom and a dome shaped wall extending upwardly from the bottom. The inner cowling is seated in the outer cowling, whereby an annular chamber is formed between the upwardly extending walls of the cowlings for redirecting the discharged air from the impeller. The impeller is disposed between the bottoms of the cowlings and is in communication with the annular chamber. 
   The support frame of the suction module preferably includes a support plate supporting the vacuum unit and fixed to the hinge assembly and a flexible skirt extending downwardly from the support plate. The support plate is preferably connected to the skirt by a flexible joint. The flexible joint allows for a relative displacement between the support plate and the flexible skirt to enhance sealing of the skirt against a surface. 
   Each of the suction modules further preferably includes at least one drive wheel provided on the support frame for translating the suction module across a surface. More preferably, each of the suction modules includes two independently controlled drive wheels provided on the support plate in a coaxial arrangement and a castor wheel rotatably supported on the support plate 
   As a result of the present invention, a wall climbing robot is provided, which utilizes aerodynamic attraction technology to achieve balance between strong attraction force and maneuverability. The new sealing and rim isolation system makes the robot flexible to go over uneven surfaces, and further allows for wall-to-ceiling and wall-to-wall transitions. The robot of the present invention can carry double the payload of conventional wall climber robots, such as the vortex climber. 
   The preferred embodiments of the wall climbing robot of the present invention, as well as other objects, features and advantages of this invention, will be apparent from the following detailed description, which is to be read in conjunction with the accompanying drawings. The scope of the invention will be pointed out in the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of the climbing robot of the present invention traversing two surfaces forming an inner corner. 
       FIG. 2  is a side view of the climbing robot of the present invention traversing two surfaces forming an outer corner. 
       FIG. 3  is a bottom plan view of the first suction module shown in  FIGS. 1 and 2 . 
       FIG. 4  is a top perspective view of the second suction module shown in  FIGS. 1 and 2 . 
       FIG. 5  is a cross-sectional view of the vacuum rotor unit of each suction module. 
       FIG. 6   a  is a schematic cross-section of a suction module illustrating the flexible joint with the vacuum rotor unit turned off. 
       FIG. 6   b  is a schematic cross-section of a suction module illustrating the flexible joint with the vacuum rotor unit turned on. 
       FIG. 7  is a top perspective view of an alternative embodiment of the climbing robot of the present invention. 
       FIG. 8  is a top perspective view of the robot shown in  FIG. 9  traversing two surfaces forming an inner corner. 
       FIG. 9  is an electrical schematic diagram of the DSP-based control system of the present invention. 
       FIG. 10  is a block diagram of the control system of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring first to  FIGS. 1 and 2 , the wall climbing robot  10  of the present invention generally includes at least two suction modules  11  and  12  pivotably connected together by a hinge assembly consisting of a bracket  13  and hinge  14  arrangement. In particular, a bracket  13  can be fixed to a first suction module  11  and a hinge  14  can be fixed to a second suction module  12 . The bracket  13  and hinge  14  are connected together about a pivot point  16 , which allows the first suction module  11  to pivot with respect to the second suction module  12 . Each suction module of the climbing robot  10  can be designed to operate independently, as shown in  FIGS. 1 and 2 , or several wall climbing robots  10  can be configured to form a larger robot that will be able to carry more payloads for complex tasks. 
   The design of the wall climbing robot  10  can be divided into four main components. The first component involves the locomotion mechanism, which is responsible for the planar motion of the robot  10  on a surface. The second component involves the transition mechanism, which is needed to connect the suction modules  11  and  12  and to achieve wall-to-wall transitions. The last two components are the adhesion mechanism and the vacuum chamber seal. Combined together, these components enable the robot  10  to “stick” to wall surfaces. 
   Referring additionally to  FIGS. 3 and 4 , the locomotion mechanism involves an internal three wheel drive provided on each suction module  11  and  12 . In particular, each suction module  11  and  12  is provided with two drive wheels  18  and one castor wheel  20 . The drive wheels  18  and the castor wheel  20  are rotatably supported on a centrally disposed support plate  22 . The drive wheels  18  and the castor wheel  20  are preferably arranged in a triangle with the drive wheels being coaxial. Each drive wheel  18  is individually controlled by a drive motor  24  fixed to the support plate  22 . The drive wheels  18  rotate about a single common axis, while the castor wheel  20  is permitted to rotate about multiple axes. Thus, each suction module  11  and  12  utilizes a differential drive principle, wherein the left and right drive wheels  18  are controlled independently and the robot turning angle is determined by the speed difference between the motors  24  driving the two drive wheels. 
   Such wheeled locomotion allows for quick motion of the robot  10  on planar surfaces. However, in order to enable the robot  10  to transition from one surface to another nonplanar surface, a transition mechanism is provided. The transition mechanism involves an articulated structure connecting the two wall-climber modules  11  and  12  together to achieve smooth transitions between nonplanar surfaces. As mentioned above, this articulated structure involves a “tilt/lift-hinge” sub-assembly including a bracket  13  fixed to the first suction module  11  and a hinge  14  fixed to the second suction module, wherein the bracket and hinge are connected about a common pivot point  16 . A hinge motor  26  is fixed to the bracket  13  and includes a rotating drive shaft  28  fixed to the hinge  14 . Thus, operation of the hinge motor  26  causes the hinge  14  to pivot with respect to the bracket  13 . Such pivoting causes the first suction module  11  to move with respect to the second suction module  12 . In this regard, each suction module  11  and  12  is preferably designed with a triangle shape to reduce the torque needed by the hinge motor  26  to lift one module with respect to the other module. 
     FIG. 1  shows the two suction modules  11  and  12 , wherein the bracket  13  and hinge  14  are operated in gang mode so that the modules are positioned relative to the other in a +90° orientation. Such orientation would be useful, for example, in traversing an inner corner formed between two adjoining walls or between a wall and a ceiling.  FIG. 2  shows the two suction modules  11  and  12 , wherein the bracket  13  and hinge  14  are operated in gang mode so that the modules are positioned relative to the other in a −90° orientation. Such orientation would be useful, for example, in traversing over an outer corner or edge of a structure. 
   Responding to electronic controls, the drive motors  24  and the hinge motor  26  can perform a sequence of translation and tilting actions that would result in the pair of modules  11  and  12  navigating as a unit between two tangent planar surfaces. The drive motors  24  and the hinge motor  26  are preferably DC servo motors with encoder feedback for precise closed-loop position control. 
   The next major design component of the present invention is the vacuum rotor unit  30  provided on each suction module  11  and  12  for providing the adhesion mechanism for the robot  10 . Referring additionally to  FIG. 5 , the vacuum rotor unit  30  includes a vacuum motor  32 , a circular impeller  34 , an inner exhaust cowling  36  and an outer exhaust cowling  38 . The vacuum motor  32  is connected to the impeller  34  for rotating the impeller about an axis of rotation  40 . Rotation of the impeller  34  draws intake air into the impeller in a direction parallel to the axis of rotation  40  and directs exhaust air out of the impeller in a direction perpendicular to the axis of rotation. 
   The inner and outer exhaust cowlings  36  and  38  are preferably, generally bowl shaped and have a radial center, which is aligned with the center of rotation  40  of the impeller  34  when assembled together. Each exhaust cowling  36  and  38  includes a bottom  36   a  and  38   a  and a dome shaped wall  36   b  and  38   b  extending upwardly from the bottom. The outer exhaust cowling  38  further preferably includes an intake hood  38   c  extending downwardly from the bottom  38   a  opposite the dome shaped wall  38   b.    
   The inner exhaust cowling  36  is seated within the outer exhaust cowling  38 , whereby an annular chamber  42  is formed between the upwardly extending dome shaped walls  36   b  and  38   b  of the inner and outer exhaust cowlings, as shown in  FIG. 5 . The impeller  34  is sandwiched between the bottoms  36   a  and  38   a  of the exhaust cowlings  36  and  38  and communicates with the annular chamber  42 . The inner exhaust cowling  36  has an opening  44  for allowing connection of the vacuum motor  32  to the impeller  34 . 
   The impeller  34  is free to rotate between the inner and outer exhaust cowlings  36  and  38  to draw inlet air from the intake hood  38   c  of the outer cowling  38 , through the bottom  38   a  of the outer cowling and into the impeller. As the vacuum motor  32  rotates the impeller  34 , the air is then redirected in a direction perpendicular to the axis of rotation  40  of the impeller into the annular chamber  44  defined by the upwardly extending dome shaped walls  36   b  and  38   b  of the inner and outer exhaust cowlings. 
   A vacuum rotor unit  30  is disposed over an opening  46  formed in the support plate  22  of each suction module  11  and  12 . The vacuum rotor unit  30  is preferably assembled to the support plate  22  so that an air-tight seal is formed between the intake hood  38   c  of the outer exhaust cowling  38  and the support plate. Air is thus drawn through the opening  46  in the support plate  22  into the intake hood  38   c  and then upward into the impeller  34 . 
   Thus, the vacuum rotor unit  30  is a radial flow device, which combines two types of airflow. The high-speed rotation of the impeller  34  causes air to be pulled upward along the spin axis  40  toward the impeller  34  creating a low-pressure or partial vacuum chamber  48  below the support plate  22 . The air drawn into the impeller  34  is then accelerated toward the outer perimeter of the exhaust cowlings  36  and  38 , away from the radial center in a direction generally perpendicular to the axis of rotation  40 . As a result of the dome-shaped walls  36   b  and  38   b  of the inner and outer exhaust cowlings  36  and  38 , the resultant exhaust air is directed upwardly toward the rear of the unit  30 , again in a direction generally parallel to the impeller axis of rotation  40 . The force of air directed on the cowling structure causes a downward thrusting force, which helps to increase the adhesion of the suction module  11  and  12  against a surface. 
   To sufficiently seal the vacuum region  48 , each suction module  11  and  12  includes a flexible skirt  50  extending downwardly from the support plate  22  in a direction opposite of the vacuum unit  30 . The flexible skirt  50  and the support plate together form a support frame  51 , which defines the vacuum chamber  48 . The flexible skirt  50  seals the vacuum chamber  48  against the surface to which the suction module  11  and  12  is adhering. The flexible skirt  50  may consist of a thin sheet of flexible plastic material, a densely packed arrangement of bristles, or a combination of the two to achieve a desirable balance between sealing and mobility. 
   In another embodiment, a compliant and flexible air inflated tube may be used instead of the skirt  50 . That is, the tube is placed around the circumference of the module and provides a sealing for the vacuum chamber, but is flexible to pass over most obstacles. The air pressure of the tube may be adjusted depending on the roughness of the traveling surface. High pressure in the tube provides good sealing, whereas low pressure makes it easier for the robot to move. Therefore, the air pressure is preferably optimized to provide a balance between good sealing and ease of robot maneuverability. This can be achieved by installing pressure sensors to monitor the pressure inside the vacuum chamber and micro-valves to control the inflation of the tube. 
   In a preferred embodiment, the flexible skirt  50  is attached to the support plate  22  with a flexible joint  52 . The flexible joint  52  is preferably made from a refoam, plastic or rubber material and is formed with a raised hinge portion  54  to further enhance flexibility. As will be discussed in further detail below, the flexible joint  52  allows for a slight displacement between the support plate  22  and the skirt  50 . This results in improved robot mobility and enhanced sealing of the vacuum chamber  48  by reducing the deformation of the skirt. The flexible joint  52  also allows the robot to maneuver over uneven surfaces with obstacles. 
   More specifically, the flexibility of the skirt  50  allows the module  11  and  12  to freely slide on rough or uneven surface, while maintaining a seal for the vacuum region  48 . The flexible joint  52  connecting the support plate  22  and the skirt  50  reduces deformation by the skirt by absorbing some of the force directed on the skirt by the vacuum unit. For example,  FIG. 6   a  shows the flexible joint  52  in a relaxed state when the vacuum unit  30  is not activated. As discussed above, when the vacuum unit  30  is activated, it exerts a downward force  56  on the support plate  22  due to the vacuum chamber  48  formed below the support plate, as well as the outlet force generated by the exhaust cowlings  36  and  38 . This downward force  56  is absorbed by the flexible joint  52  to reduce deformation of the skirt  50 , which experiences an opposite reaction force  58 , as shown in  FIG. 6   b.    
     FIGS. 7 and 8  show a smaller and more compact wall climbing robot  100  in an alternative embodiment of the present invention. In this embodiment, the wall climbing robot  100  includes two suction modules  101  and  102 , six wheels  103 ,  104 ,  105 ,  106 ,  107  and  108 , two suction system assemblies  110  and two skirt assemblies  112 . The front module  101  has a bumper  114  and the rear module  102  has a bumper  115 . The three wheels on the left side  103 ,  104  and  105  are driven together by a left drive motor  116  through two timing belts  117  and  118 . Similarly, the right wheels  106 ,  107  and  108  are driven together by a right drive motor  120  and two timing belts  121  and  122 . Thus, the left and the right drive motors  116  and  120  independently turn the left and the right side wheels in order to turn the robot to the left or to the right. 
   To climb up a wall or move from one plane to the next, there is a hinge motor  124 , which cause the two modules  101  and  102  to pivot with respect to one another. The hinge motor  124  is located at the joint between the two suction modules  101  and  102 . The left drive motor  116  is disposed on the top surface of the first suction module  101 , whereas the right drive motor  120  is located under the surface of the second suction module  102 . This arrangement allows both motors to pivot without interfering with each other, such as when the robot is transitioning up a vertical wall, as shown in  FIG. 8 . 
   The body of the hinge motor  124  is rigidly connected to the first suction module  101  through a bracket and the output of the motor is rigidly connected to a gear arrangement  125 . Upon rotation of the hinge motor  124  the first suction module  101  rotates with respect to the second suction module  102 . Similarly, the left drive motor  116  is rigidly connected to the first suction module  101  through a bracket and the output is connected to a gear arrangement, which drives the timing belts  121  and  122  and the right side drive system assembly is a mirror image of the left drive system assembly. 
   The skirt assembly  112  for each suction module is similar to that described above. In particular, each skirt assembly  112  includes a mounting bracket  126  fixed to the frame of the suction module, a skirt brush  128  extending downward and a flexible seal  130  connecting the skirt brush to the mounting bracket. In this manner, the skirt brush  128  is allowed some movement with respect to the module. The function of the skirt assembly  112  is similar to that described above. 
   The suction system assembly  110  is also similar to that described above. Specifically, each assembly  110  includes a motor  132 , an impeller  134  and an exhaust cowl (not shown in  FIGS. 7 and 8 ). The suction assembly  110  operates the same as that described above. 
   In both embodiments, the robot  10  is a self-contained system having its own power source (e.g., batteries), sensors, control system, and associated hardware. As such, it will be desirable to minimize robot weight and power consumption to prolong operation. With this in mind, the present invention preferably includes a digital signal processing (DSP) chip, or other micro-processor, to control the system. A suitable microprocessor  59  for use with the DSP-based system of the present invention is Model No. TMS320F2812 from Texas Instruments, Inc. The F2812 is a 32-bit DSP controller provides high-speed and large memory space making the real-time implementation of advanced control algorithms possible. The on-chip CAN-bus (control area network) also makes the interconnection of several wall-climber modules easy.  FIG. 9  illustrates the hardware connections based on the F2812 DSP chip. 
   As additionally shown in  FIG. 10 , the primary sensor components that are preferably provided on the robot  10  of the present invention include: pressure sensors  60 , for monitoring the pressure level inside the vacuum chamber  48 ; ultrasonic sensors  62  and infrared (IR) sensors  64 , for distance measurement and obstacle avoidance; and MARG (Magnetic, Angular Rate, and Gravity) sensors  66 , for tilt angle and orientation detection. For remote control operation, the robot  10  preferably has a wireless receiver module  68 , which communicates with the transmitter module in a remote controller  70 . 
   Apart from the above primary sensors, additional application sensors can be installed on the robot  10  as payloads when required by specific tasks. For example, a wireless pin-hole camera  72  can be installed for reconnaissance purposes, wherein video images can be transmitted to and processed at a host computer  74 . 
   The DSP controller  59  produces pulse width modulation (PWM) signals and preferably drives the motors  24 ,  26  and  32  via one or more power electronic chips. Four Motorola H-bridge chips  76  are shown, as an example. The F2812 DSP chip has two built-in quadrature encoder pulse (QEP) circuits. The encoder readings of the two drive motors  24  can be obtained using the QEP channels while a software solution can be implemented to get encoder reading of the hinge motor  26  using the Capture units of the DSP. 
   With the encoder feedback, a closed-loop control is formed to generate accurate speed/position control of the drive motors  24  and the hinge motor  26  for each suction module  11  and  12 . The speed of the vacuum motor  32  is adjusted with the feedback from the pressure sensors  60 . Using an Analog to Digital Converter (ADC), the pressure inside the vacuum chamber  48  can be monitored continuously. For example, if the pressure is lower than a threshold, the speed of the vacuum motor  32  is increased to generate more suction force. If the pressure is higher than a threshold, the speed of the vacuum motor  32  is decreased to reduce the pressure. In this manner, an ideal pressure in the vacuum chamber  48  can be maintained to keep the robot “sticking” to a surface, while at the same time maintaining robot mobility. 
   The climbing robot  10  can be operated both manually and semi-autonomously. The infrared sensors  64  can be used to measure distances from close proximity objects, while the ultrasonic sensors  62  can be used to measure distance from objects that are far away. The infrared sensor  64  preferably has a reliable reading in the range of 10 cm to 80 cm and the ultrasonic sensor  62  preferably has a reliable range between 4 cm to 340 cm. An external interrupt (XINT) channel can be connected to the ultrasonic sensor  62  to measure the time-of-fly of sound chirp and convert the measurement to distance reading. 
   In order for the climbing robot  10  to understand its orientation and tilt angle, the MARG sensor  66  can be composed of nine sensor components of three different types affixed in X-Y-Z three axes: a magnetic sensor  66   a , an accelerometer  66   b , and a gyro  66   c . The magnetic sensors  66   a  allow the robot  10  to know its orientation with respect to a reference point (i.e., the north pole). The accelerometers  66   b  measure the gravity in three axes and thus provide tilt angle information to the robot  10 . The gyro sensors  66   c  measure angular rates which are used in the associated filtering algorithm to compensate for dynamic effects. The DSP controller  59  preferably processes the inputs from the nine MARG sensor components via ADC and provides the robot with dynamic estimation of three-dimensional orientation. 
   There are preferably two ways the DSP controller  59  communicates with external sources. The host computer  74  can exchange data with the DSP controller  59  via serial communication interface (SCI) using RS232 protocol. Another source that can send commands to the DSP controller  59  is the radio remote controller  70 . This can be accomplished by interfacing the receiver  68  with a decoder  76  and then translating the commands into a RS232 protocol compatible with SCI module. 
   Other blocks shown in  FIG. 10  represent possible on-board software modules including a command interpreter  78 , a task level scheduler  80 , a trajectory planner  82 , a motor controller  84  and a motion planner  86 . The operator commands, such as “move forward” and “make left turn” are transmitted from the remote controller  70  held by a human operator and decoded by the on-board command interpreter  78 . The generated task level commands are then fed into the task level scheduler  80 . The task level scheduler  80  uses a finite state machine to keep track of robot motion status and refine the command into several motion steps. The trajectory planner  82  interpolates the path to generate a set of desired joint angles. The digital motor controller  84  then drives each motor  24 ,  26  and  32  to the desired set points so that the suction modules  11  and  12  move the robot  10  to the desired location. 
   The robot  10  can also have motion planning ability, wherein the motion planner  86  generates a feasible motion sequence and transmits it to the task level scheduler  80 . After the motion sequence has been executed, the robot  10  is able to travel from its initial configuration to its goal configuration, while avoiding any obstacles in the environment  88 . 
   As a result of the present invention, a wall climbing robot is provided, which utilizes new concepts of modularity and mobility for moving from ground to vertical wall, wall to ceiling and between surfaces. The wall-climbing robot of the present invention includes a novel design for the adhesive mechanism to ensure that the robot can navigate on essentially any kinds of wall surfaces, such as brick, wood, glass, stucco, plaster, gypsum board, and metal. A new flexible bristle skirt provides sealing and mobility through a pressure force isolation rim connecting the vacuum plate and the bristle skirt. The robot also has a modular and reconfigurable mechanical design which combines wheeled locomotion and articulated structure to achieve both quick motion and smooth transition between two inclined surfaces. The robot further includes a DSP-based embedded system which integrates sensing, control, planning and makes the real-time implementation of advanced control algorithms possible. 
   One potential application of the wall-climbing robot system is in the area of inspection and maintenance. For example, the robot can be utilized for routine inspection of buildings, bridges, nuclear containment domes, city pipelines, and other hazardous areas or hard-to-reach places. Maintenance applications may, for example, include sand blasting of ship hulls, etc. Other civilian applications may include transport of small items to hard-to-reach or hazardous locations, assistance in firefighting and search &amp; rescue operations, etc. 
   The robot of the present invention is also well suited for urban warfare applications. Such applications may, for example include surveillance and reconnaissance, weapon delivery, guarding a perimeter around a building, decoy applications on battle fields, etc. 
   Security and counter-terrorist applications are also well within the capabilities of the present invention. These tasks may, for example, include intelligence gathering about a hostile situation within a building, intelligence gathering from a ventilation duct, assistance in hostage rescue operations, etc. 
   Although preferred embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments and that various other changes and modifications may be affected herein by one skilled in the art without departing from the scope or spirit of the invention, and that it is intended to claim all such changes and modifications that fall within the scope of the invention.