AISC 351 - Small Remotely Operated Screw-Propelled Vehicle

Small Remotely Operated Screw-Propelled Vehicle

Dymitr Osiski and Ksawery Szykiedans

Faculty of Mechatronics, Warsaw University of Technology, Warsaw, Poland{d.osinski,k.szykiedans}@mchtr.pw.edu.pl

Abstract. This paper concerns a small remotely operated screw-propelled ve- hicle that was a topic of a master thesis tilted Design of screw-propelled ve- hicle. It begins with introduction, which briefly overviews basic features and applications of screw-propelled vehicles. The second chapter describes in detail designed remotely operated vehicle. The third chapter is focused on the simula- tion model of the vehicle implemented in Matlab-SIMULINK environment. The last chapter concludes the work done.

Keywords: screw-propelled vehicle, screw propulsion, spiral propulsion, auger driven, helical drive, screw rotor, remote controlled vehicle.

1 Introduction

1.1 Basics of Screw-Propelled Vehicles

Vehicles with wheels, continuous tracks or legs are commonly used in various engi- neering tasks. Screw-propelled vehicles are scarce and not a common sight. Such vehicles employ at least one drive screw as a mean of locomotion. Drive screw is usually a cylinder with a helical blade, similar to screw thread, which can rotate around its longitudinal axis. The most widely used configuration employs two parallel drive screws with opposite helix directions (one helix is clockwise, while the other is counter-clockwise). Design of a screw-propelled vehicle designs is not limited to the two screw configuration. While many screw-propelled vehicles use a number of pairs of drive screws, there are also vehicles that employ an odd number of drive screws, as well as vehicles using both drive screws and other means of locomotion, such as wheels, skids or continuous tracks. Some of the designs make it possible to change orientation of the drive screws with respect to vehicles frame in order to enhance the maneuverability.Screw-propelled vehicles are able to operate in a difficult terrain. They can traverse soft, muddy ground or deep snow cover. Some of the designs are amphibian, which allows them to operate in water, with drive screws working in a similar manner to boat propellers. Screw-propelled vehicles usually develop a high tractive force. Another feature is a simple design and low number of moving parts, especially when compared with other means of locomotion in difficult terrain, such as tracked ve- hicles. The main disadvantages of screw-propelled vehicles are low maximum speed and high power required due to significant energy losses. Moreover, such vehicles are difficult to operate on rigid surfaces and can possibly damage surfaces they move on.

Springer International Publishing Switzerland 2015R. Szewczyk et al. (eds.), Progress in Automation, Robotics and Measuring Techniques, Advances in Intelligent Systems and Computing 351, DOI: 10.1007/978-3-319-15847-1_19 191

D. Osiski and K. Szykiedans

Small Remotely Operated Screw-Propelled Vehicle

The most notable screw-propelled vehicles are the American Marsh Screw Amphi- bian and Russian ZiL-29061. Marsh Screw Amphibian, developed by Chrysler in1960s, was meant to be a utility terrain vehicle, but due to the behavior of screw pro- pulsion on a rigid terrain was not considered a success. The ZiL was designed in1970s as a rescue vehicle for cosmonauts that landed in inaccessible areas. Nowadays, Australian vehicle MudMaster is used as a mean of dewatering and densification of soil. The three vehicles are similar in size to a truck. Smaller screw-propelled vehicles have also been developed. Spiral Track Autonomous Robot designed at Lawrence Livermore National Laboratory is a survey vehicle intended to operate in hostile envi- ronments. The Screw Drive Rover, developed at the Graduate University for Ad- vanced Studies (Sokendai) in Japan was used as a help in validating simulation of interaction between soil and drive screw. Remotely controlled screw-propelled ve- hicle was presented by Tyco toy company under the name of Terrain Twister. All of the mentioned vehicles employ configuration of two parallel drive screws. Russian company Tesh is working on improving the operation of screw-propelled vehicles on rigid ground by combining the drive screws with rubber tires. When the vehicle is operating on soft soil, the tires are deflated and the helixes of drive screws are in con- tact with the ground. The tires can be inflated to work on rigid ground like standard tires.

Fig. 1. Illustration of several screw-propelled vehicles, approximately to scale. From top left: MudMaster, ZiL-29061, Marsh Screw Amphibian, Spiral Track Autonomous Robot, Screw Drive Rover, Terrain Twister

1.2 Principle of Operation

When the drive screw is rotated, the helix is pushed against the ground, what results in reaction forces acting on the screw blade. The normal force is large, as the ground cannot easily overstep the helix blade, while the tangent force is small, as the ground can easily slide along the helix blade.

Fig. 2. Basic forces acting on helix blade, expanded view. Fn normal force acting on screw blade, Ft tangent force acting on screw blade, helix angle, hatched rectangle screw - ground contact area, gray line screw blade edge.

The dominant normal force can be expressed as two components longitudinal and lateral. In the case of two parallel drive screws the angular velocities of the screws may be adjusted, so that the lateral components counteract each other, while the longi- tudinal components add up. As a result, the vehicle can move forward. Varying the angular velocities can result in a change of vehicle velocity and direction of motion. Depending on the angular speed of the helixes (and other factors, such as terrain con- dition), a screw propelled vehicle can move forward, backward, sideways and turn.Torques acting upon the drive screw are torque developed by the motor driving the screw, friction torque of the screw bearings, torque of the lateral components of forces between the ground and the screw (usually acting upon the helix, but in the case of a soft ground the forces can also act upon the drum of the drive screw) and resultant torque dependent on angular acceleration and mass moment of inertia of the drive screw.

Fig. 3. Components of the normal force acting upon the helix blade of a screw-propelled ve- hicle. Only two normal forces are illustrated. Fnl, Fnr normal forces acting upon the left and the right screw blade, Flonl, Flonr longitudinal components of normal forces acting upon the left and the right screw blade, Flatl, Flatr lateral components of normal forces acting upon the left and the right screw blade, l, r angular velocities of the left and the right drive screws.

The surface on which a screw-propelled vehicle operates affects its movement abil- ities. On a rigid surface, when the screws are rotating in the same direction, the ve- hicle may roll sideways the area of contact between the drive screw and the ground is very small, and the screws act as a set of wheels. In a similar scenario of co-rotating screws, but on a soft ground, the vehicle may rotate around its vertical axis due to large normal forces acting upon the helix blade submerged in mud, and will hardly roll sideways.

2 Design of the Screw-Propelled Vehicle

2.1 Design Assumptions and Requirements

The design assumptions and requirements related to the vehicles functionality, oper- ating environment and the user were formulated, giving a brief overview of the neces- sary functions and features of the device. The most important are listed below. The designed screw-propelled vehicle was expected to be small, with the length, width and height limited to 500 mm 400 mm 300 mm, and not heavier than 5 kg. It had to employ at least one drive screw as a mean of locomotion and be able to traverse difficult terrain such as mud. The maximum speed required was 50 mm/s.

2.2 Details of the Vehicle

A concept of remotely operated screw-propelled vehicle with two parallel drive screws was chosen to be designed. Review of possible technical solutions was rea- lized, with each possible solution followed by a list of its advantages and disadvan- tages, allowing one to choose the components which meet the relevant requirements. The vehicle was designed with the aid of Autodesk Inventor and AutoCAD software. The three-dimensional model of the vehicle model was used as a basis for creation of two-dimensional technical documentation in a form of engineering drawings.

Fig. 4. Kinematic scheme of the screw-propelled vehicle. Standard symbols depict toothed belt transmissions, plain bearings, beam couplings and shafts.

The screw-propelled vehicles length, width and height are 348 mm 256 mm 177 mm. Its mass is 4.5 kg. The drive screws are located on the left and right side of the main body. The main body supports all electric and electronic components. Low height of the vehicle increases its stability, while the relatively large width helps turning.

The drive screws are symmetric, both are 254 mm in length. The outside diameter of drive screws is 70 mm, helix angle is 30. The right screw is clockwise, the left is counter-clockwise. Height of the screw blade is 10 mm and its thickness is 1 mm. The drum is made of 50 mm in diameter, 1 mm thick steel, chrome-coated pipe. Blades are welded to the pipes. Shafts of the drive screws are mounted in polymer plain bearings.

Fig. 5. Three-dimensional model of the screw-propelled vehicle

Mechanical power generated by two Modelcraft RB350050 brushed DC motors with gearheads is transferred to the drive screws by means of beam couplings and toothed belt transmissions, located at the rear of the vehicle. The DC motor provides a maximum torque of 5.39 Nm and maximum rotational speed of 120 RPM. The pul- ley shaft is supported in polymer plain bearings, just as the to drive screws. Gear ratio of the belt transmission is 2.5.The DC motors are powered by REDOX 1800 mAh 11.1 V 20 C lithium-polymer battery, controlled by two AVT5190B electronic speed control units. The units have a built-in battery protection and over-temperature protection. One of them powers an EK2-0420A 35 MHz receiver. The operation time of the vehicle depends on the motor load and should be at least 12 minutes.The main body is made of 2 mm thick sheet metal, bent in order to increase its stiffness. The front of the vehicle contains an additional L-shaped sheet, while the rear has a S-shaped sheet that supports the DC motors and the pulley shafts. The body is powder coated. The body was to be protected with a clear polymer case with two radiators on sides, but at present only a provisional case is available.User can operate the vehicle by using E-Sky EK2-0404 remote control transmitter. Two channels are used to independently control angular speed of the drive screws.

Fig. 6. Photography of the designed screw-propelled vehicle without case, top-down view

3 Simulation Model of the Screw-Propelled Vehicle

3.1 Implementation in Matlab-SIMULINK Environment

The simulation model is based on equations of motion and forces equilibrium. It de- picts a screw-propelled vehicle with two parallel drive screws with opposite helix directions and pitch constant along its axis. The screws can rotate independently and can also be hinged, with the hinge located in the middle of each screw. The vehicle is able to move on a plane and has 3 degrees of freedom two components in transla- tion and one angle of rotation. The chosen assumptions and simplifications allowed the mathematical model to remain fairly simple, while simultaneously providing a model that depicts the movement of the screw-propelled vehicle in a reasonably realistic way.The mathematical model was implemented in Matlab-SIMULINK environment. In order to obtain velocity and position of the vehicle, the translational and rotational accelerations of the vehicle are integrated twice. The output data contain position of the vehicle center of mass, its heading and lateral and longitudinal components of vehicle velocity.

3.2 Exemplary Results of the Performed Simulations

Due to high number of tests performed and a limited volume, only three examples of simulation results are presented in this chapter. Only the most important of user- selectable simulation parameters relevant in these three cases are shown. In each test, the vehicle starts in the center of Cartesian coordinate system. Initial translational and rotational velocities are equal to zero. Each simulation study lasts for 10 seconds.

Contra-rotating Drive Screws

Fig. 7. Results of simulation of motion for contra-rotating drive screws. From the left: plot of vehicle position, plot of vehicle forward velocity vs. time and illustration of the configuration of the drive screws.

angular velocity of the left and the right drive screw: 6.28 rad/s and 6.28 rad/s helix angle of the left and the right drive screw: 30

The screw-propelled vehicle moves forward, accelerating until it reaches a maximum velocity dependent on angular velocity of the drive screws, helix pitch and friction.

Co-rotating Drive Screws

Fig. 8. Results of simulation of motion for co-rotating drive screws. From the left: plot of ve- hicle position, plot of vehicle heading vs. time and illustration and illustration of the configura- tion of the drive screws.

angular velocity of the left and the right drive screw: 6.28 rad/s and 6.28 rad/s helix angle of the left and the right drive screw: 30

The vehicle moves sideways while simultaneously turning.

Hinged, Co-rotating Drive Screws

Fig. 9. Results of simulation of motion for hinged co-rotating drive screws. From the left: plot of vehicle position, plot of vehicle heading vs. time and illustration of the configuration of the drive screws.

angular velocity of the left and the right drive screw: 6.28 rad/s and 6.28 rad/s helix angle of the left and the right drive screw: 30 hinge angle of the left and the right drive screw: 30 and 30

Employing the hinging feature of the drive screws allows the vehicle to turn when rolling sideways, enhancing its mobility when moving on a rigid surface.

4 Conclusion

The paper outlines most important parts of the master thesis focused on design of screw-propelled vehicle. It begins with a description of features and applications of screw-propelled vehicles. It also overviews the principle of operation of such ve- hicles. The basic design assumptions and requirements in regard to the vehicles func- tionality are stated, followed by a description of the designed screw-propelled vehicle. The simulation model implemented in Matlab-SIMULINK environment is briefly described, with examples of three performed tests. The designed remotely operated screw-propelled vehicle fulfills the given requirements. The results of simulation could be verified by a comparison with a real screw-propelled vehicle. The simulated vehicle can move in similar manner to its real word counterpart, indicating that both the mathematical model and its implementation are correct.

References

1. Freeberg, J.T.: A Study of Omnidirectional Quad-Screw-Drive Configurations for All- Terrain Locomotion. University of South Florida, Tampa (2010)2. Knight, S.J., Rush, E.S., Stinson, B.G.: Trafficability Tests with the Marsh ScrewAmphibian on Coarse-Grained and Fine-Grained Soils. US Army Engineer WaterwaysExperiment Station, Vicksburg (1964)3. Kress, R.F.: Design Manual for Buoyant Screw Propulsion. Chrysler Corporation DefenseOperations Division, Detroit (1965)

D. Osiski and K. Szykiedans

D. Osiski and K. Szykiedans

4. Liu, Q., Hayasaka, Y., Hanajima, N., Kawauchi, K., Yamashita, M., Hikita, H., Kazama, T.: Development of a Spiral Propulsion Mechanism in Wetlands Relation between Torque and Load. Muroran Institute of Technology, Muroran (2009)5. Nagaoka K.: Study on Soil-Screw Interaction of Exploration Robot for Surface andSubsurface Locomotion in Soft Terrain. Graduate University for Advanced Studies(Sokendai), Hayama (2011)6. Residue Solutions MudMaster,http://www.residuesolutions.com.au/services/mudmasters7. The Spiral Track Autonomous Robot,http://www.pbs.org/wgbh/nova/robots/hazard/meetstar.html8. Off-road Vehicle ZiL-29061, http://sersarajkin.narod2.ru/ALL_OUT/TiVOut10/SKBZIL55/ SKBZIL55042.htm (in Russian)