Possibility of the Kinematics Arrangement of a Mobile Mechatronic System

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A trend in the robotics development for the next millennium assumes generally its significant expansion into other than mechanical fields and non-production areas. This fact creates technical and operational conditions for applications and defines requirements on technical means for robotization and automatization within a large scope of services and servicing activities connected with that were not possible until now from the point of view of the onset of classical robots for such tasks. ^[1].

3. Wheeled Mobility Systems

All mobile service, those subsystem mobility is solved on the principles flywheel undercarriage belong in this part.

The most common form of vehicle layout is the four-wheeled, front-steer vehicle. It is a descendant of the horse-drawn wagon, but major changes has undergone some subtle and some. A motor was added to replace the horses in the many decades since. The suspension and steering systems were the most important changes ^[2].

Figure 2. Space of application service robots [1]

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3.1. One-wheeled Layouts

The most basic vehicle would have the least number of wheels. One-wheeled vehicle has limited mobility, but can get around relatively benign environments. An actually ball is wheel with an internal movable counterweight that, when not over the point of contact of the ball and the ground, causes the ball to roll. With some appropriate control on the counterweight and how it is attached and moved, the vehicle can be steered around clumsily. The ability is limited and depends on what the actual tire is made of, and the weight ratio between the tire and the counterweight ^[2].

Single-wheel platforms, on the other hand, are not statically stable - they fall without support. To provide stability and usability you'd have to solve quite challenging engineering problems.

Figure 3. One wheel robot [4]

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Solving complicated engineering problems is good for humanity. Dynamically stable single wheel robots have a potential to become very agile and compact. Thus - ideal to use in crowded environments in interaction with humans.

A single wheel robot could be a cheaper solution for a robot receptionist who has to work on one floor only. ^[4].

Figure 4. One wheel robot [3]

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3.2. Two-wheeled Layout

Its exist two obvious, wheels fore and aft, and side by side wheels. The bicycle is perhaps one of the most recognized two-wheeled vehicles in the world. It is quite difficult for robots to use, because it is not inherently stable. The side by side layout is also not inherently stable, but is easier to control ^[2].

To drag a passive leg or tail behind the vehicle is the second less obvious layout.

Figure 5. Drag tail [2]

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The torque produced by the wheels counteracts this tail, makes the vehicle statically stable, the height of obstacle the robot can get over ^[2].

Figure 6. Tail dragger [5]

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Dean Kamen developed the Segway two-wheeled balancing vehicle, proving it is possible, and is actually fairly mobile.

Figure 7. Segway [6]

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3.3. Three-wheeled Layouts

Three wheels can be laid out in several ways. The most common and easiest to implement, but with, perhaps, the least mobility of the five three-wheeled types, is present by a child´s tricycle. Robot destines to be used indoors, in a test lab or other controllable space ^[3].

Figure 8. WowWee Rovio [7]

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3.4. Four-wheeled Layout

A significant position in the statistics of the currently applied wheel mobile service robot is robots on a four-wheel carriage occupy. This robots are the most used ones overall. They proved themselves successfully almost in all areas of service robot application ^[1].

Figure 9. All four fixed, fix steered [2]

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The most basic four-wheeled vehicle actually doesn’t even use a differential. It has two wheels on each side that are coupled together and is steered just like differential steered tricycles. Skid Steer - its name this steering method.

Greater mobility is achieved if the center joint also allows a rolling motion between the two sections. This degree of freedom keeps all four wheels on the ground while traversing uneven terrain or obstacles. It also improves traction while turning on bumps. Highest mobility for this layout would come from powering both the pivot and roll joints with their own motors and each wheel individually powered for a total of six motors. Alternatively, the wheels could be powered through limited slip differentials and the roll axis left passive for less mobility, but only three motors.

An unusual and unintuitive layout is the five-wheeled drivetrain. This is basically the tricycle layout, but with an extra pair of wheels in the back to increase traction and ground contact area. The front wheel is not normally powered and is only for steering. ^[2].

Figure 10. Two-section connected through vertical joint [2]

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The longitudinal rocker design divides the entire vehicle right down the middle and places a passive pivot joint in between the two halves.

Figure 11. Simple longitudinal rocker [2]

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This joint is connected on each end to a rocker arm, which in turn carry a wheel at each of their ends. This layout allows the rocker arms to pivot when any wheel tries to go higher or lower than the rest. This passive pivoting action keeps the load on all four wheels almost equal, increasing mobility simply by maintaining driving and braking action on all wheels at all times.

Figure 12. GTR 2010

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Longitudinal rocker designs are skid steered, with the wheels on each side usually mechanically tied together like a simple skid steer, but sometimes, to increase mobility even further, the wheels are independently powered. Many of the wheeled layouts are complex enough that they require a motor for every wheel. Although this seems like a complicated solution from an electrical and control standpoint, it is simpler mechanically. ^[2].

3.5. Six-wheeled Mobile Service Robot

Beyond four- and five-wheeled vehicles is the large class of six-wheeled layouts. There are many layouts, suspensions, and drivetrains based on six wheels. Six wheels are generally the best compromise for high mobility wheeled vehicles. Six wheels put enough ground pressure, traction, steering mobility, and obstacle-negotiating ability on a vehicle without, in most cases, very much complexity. The most basic six-wheeled vehicle, shown in Figure 9, is the skid-steered non-suspended design. This is very much like the four-wheeled design with improved mobility simply because there is more traction and less ground pressure because of the third wheel on each side. The wheels can be driven with chains, belts, or bevel gearboxes in a simple way, making for a robust system.

Figure 13. Six wheels, all fixed [2]

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Figure 14. Six - wheeled robot. [8]

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