Report on the Design spider robot

This project will be making use of some of the mechanical engineering concepts for formation of a moving robot. This project aims to formulate a moving robot having a four-bar linkage. This project also aims to identify the accurate procedure for constructing an efficient robot design. It is required in the project to consider a design that includes a four-bar linkage besides a motor and body. The project initiates with determining the length and width of the links and their connection with each other within the robot. Moreover, there must be alignment of robot’s body and the links so as to ensure smooth movement of the robot. The robot design must contain a motor attached to shaft and gears to allow the robot to move and walk. In the present work, the main process of development of a legged robot is considered with the consideration of needed features. The four-legged spider robot work under the control of the communication port on computers. The main concepts are taken by inspiration from spider and developed with a maximum control mechanism that executes various walking behavior. The performance is evaluated to identify the effect on rough terrain by having four legs like spiders. The motion is flexible that is designed with functional algorithms against different conditions such as pit and rough terrain. Similarly, the algorithms are designed to move the spider at different levels of speed that are related to the stability at four legs.

Literature review of Design spider robot

Various parts are involved in the formation of a moving robot with four-bar connection. The principal parts of such a robot are the exterior frame of the robot which includes the entire design of the robot and the interior connections within the frame to connect various parts of the robot. Besides these parts, the robot also consists of the motor accompanied by gears and shaft for operating robotic structure. The robot has output links that facilitate the movement of the robot in a particular direction [1]. At the beginning of this project, the equations and theories related to robotics are studied. The linkage robot refers to the robot wherein the links are established between various parts of robot to balance various forces and allow the robot to move smoothly [2]. In such a robot, the linkages must have accurate dimensions; otherwise the robot’s movement may get affected. Since this is a moving robot, the principal components of this design are the legs of the robot. The dimensions and weight of the legs and location of joints are the main aspects of consideration in this kind of robot. Besides these factors, another significant factor is the angle of rotation of the leg which needs to be appropriate to ensure the balancing of the robot body during its movement [3]. The analysis of the robot design can be done using the following equations [4], Grubler & Kutzbach Equation will be used to find the Mobility (DOF). This equation is given as follows:

Where: M denotes the DOF or mobility L denotes the number of links J1 denotes the number of 1 DOF (full) joint J2 denotes the number of 2 DOF (half) joint.

Using Grashof Equation,

Where: S denotes the length of the smallest link L denotes the length of longest link P denotes the length of one remaining link Q denotes the length of another remaining link

Figure 1: Four-bar mechanism.com

The robot’s weight is a significant factor that needs to be considered during the formation of robot. it has an impact on the robot’s movement and balance of legs and body during movement. Appropriate weight of robot is essential for stable and balanced movement of robot’s legs [5]. Another factor that holds significance while designing a robot is its motor. Appropriate size and power of the motor is essential for smooth operations of the robot. Usually, Micro gear 9v DC motor is appropriate for the fast and smooth walking of the robot [6]

The development is based on the technology used in the working process, speed of robots, stability, and functions. Berns et al (1993) designed a fundamental camera-based local robot that was used for the navigation of LAURON III. Parlaktuns et al (2007) designed an ultrasonic sensor-based model that worked for the calculation of distance value with the usage of acoustic wave motion. Margolis et al (2018) developed a robotic system that used the technology of Arduino and each leg of the robot was commanded by the microcontroller (Tolga Karakurt, 2015).

Project progress of Design spider robot

This project involves the manual formation of model-walking robot. The main concept focuses on the formation and structure of the robot legs and their movement which is facilitated by the robot’s joints besides other parts. The foremost step in the robot formation involves its sketching on the paper. The model of this walking robot has two designs. Considering the first design, a few steps had to be followed to formulate the robot structure on the paper. These steps include the sketching step whereby the basic design of the robot’s body part specifically its legs are drawn. This design is  based on 6- leg structure. Moreover, the robots profile and its size, the joints and the angle at which these joints move are depicted below:

Figure 2: First design

This design basically includes 6 legs that are attached to the robot’s body. Moreover, there are four joints at each side of the robot. Certain drawbacks were found to be associated with this kind of design such as the connection of motor to each link and lower degree of flexibility in the robot. The second robot design involved in this project is basically a four-leg structure with all the legs attached to linkage to facilitate the robot’s movement. Each side has 2 legs. This robot is called the four-bar linkage walking robot. This robot has a body attached to a small-sized shaft as well as gears. The motor is located in the middle of the robot.

Figure 3: Second design

The second design considered in this project is a four-legged walking robot with a couple of joints at each leg. The factors that are significant in such a robot are the size and shape of the motor, the angle of rotation of the legs and the joints. The subsequent step of this project involves the sketching of the robot with the help of SolidWorks. It must be noted that the size of the legs and body must be kept such that the motor can be installed in between them. There were some issues and complications in the sketching of this design due to the wrong computation of the part of body attached to motor which called for the re-modelling of that part. Finally, the project preferred to use the second design since this design ensures higher degree of mobility and appropriate size of motor. The project uses an ultrasonic sensor for the detection of hurdles and obstacles faced during the motion of the new spider robot. The ultrasonic sensor model measures the distance and barriers were detected through the mechanism of emitting acoustic wave through the ultrasonic sensor. The main body consists of lightweight composite material that is cost-effective and durable. Therefore, while moving, the robot kept the balance by itself. In the front side of the body, the power switch, battery and ultrasonic sensor are embedded with two control circuits, Bluetooth, and camera.

Current design of Design spider robot

The selection of the appropriate design, dimensions and joints is followed by this step which involves the connection of motor with the legs and joints of the robot. The connection of motor to robot legs and joints is done as decided earlier. The computerized solid-modelling design known as SolidWorks is used for designing the robot. The process involves determining 8 link bars which serve as the robot’s legs. For this purpose, a 3D printer will be employed. This is followed by sketching the joints that serve as a connection between legs and the shaft with the help of a laser printer. The final step is the assembling of parts to reveal the structure of a walking robot. The mobility equation shown below is used to ensure that the created linked structure enables the robot to move and walk:

These results clearly indicate that the shortest link can move freely.

After deciding to go with selected design, the design was drawn using Solidworks and then imported to Solidworks technical drawing to make a clearer picture with description of every part. The figure below provides solid information about the design:

Figure 4: CAD

Moreover, the 3D printer located at QUT Institute was employed to compose the robot and legs (shown below) using plastic material.

Figure 5: Robot parts

The following figure depicts the ultimate assembled design of the robot:

Figure 6: Robot after assembly

The control unit work based on Arduino technology and each leg of the spider robot is provided with a microcontroller. PWM signals pass through the output of the Arduino board and transmitted over the connector to servo motors. The commands are entered by computer for locomotion and then transmitted over Bluetooth. The camera provides images of the location and controls the robot as an IP camera (Spenneberg, et al., 2005). The mobile robots are supposed to be efficient regarding the high performance and power resource usage. For this purpose, the weight of the materials used in the infrastructure of the robot should be considered twice. The use of a minimum number of actuators is required for design under a suitable mechanism. The walking algorithm is developed with critical evaluation for the flexibility control and functionality of the robot (Santos, Garcia, & Estremera, 2018). During motion, the obstacles are detected by the ultrasonic sensor. The design sample was transferred to the control board from the actuator and then rotated at certain angles and routed unimpeded. The location of the ultrasonic sensor in the four-legged spider robot is in the front of the robot as illustrated in figure 7.

Figure 7: Ultrasonic sensor that is placed on the front of the robot to detect

Similarly, the camera has its data bus that controls the IP of the camera (Teli, Agarwal, Bagul, Badawane, & Bandre, 2019). The leg coordination is required for the sustainable motion without falling therefore walking can be complication while working. The walking algorithms are designed to strengthen the gait pattern. The wave gaits work over only one leg to make it in swing phase (Morita & Ishihara, 2009). Three moves are designed for the level of speed, so the algorithm of motion provides a variety of style. Considering the velocity status, biped gaits exist between the explorer gait and tripod. The advantages of the design are the combination of legs that were analyzed by the experimental results. The analysis of the motion and velocity of tripod gait was measured as 0.065 m/sec. The purpose of the motion and testing of flat ground is related to the detection speed. The calculated results obtained from the theoretical analysis of the motion of spider robot are mainly related to the walking algorithms and parameters of step length, distance, time, velocity and degrees for each type of gaits of the four-legged spider robot. The gait types in the present analysis were explorer, tripod, wave, and biped. Biped leg coordination can be illustrated as the progressing motion of the robot by the pair of legs. The robot first moves on two legs and legs propel the body in the forward detection. In case of the velocity status, biped gait exists between the explorer gait and tripod gait. The explorer gait is somehow similar to the motion of wave that is linked with running series of legs. Both types of gaits are then controlled through the sequence motion. The algorithm is designed for slow and fast motion and sensitive legs (Shahriari, 2013). Always, two legs propel the body towards the selected direction. The gait is then preferred highly through the rough terrains. The speed of robot is improved with dynamic analysis and angular velocity of the robot can be measured as

The above formula of angular velocity of the robot is used for theoretical evaluation of the speed of robot. The rotation speed of the motor determines the movement of legs and reduced number of legs improve stability of robot.

Material sources of Design spider robot

There are a variety of materials that can be used to construct a robot. However, the most preferred material in this regard is plastic due to certain qualities of this material. The main attribute of the plastic that is considered to be favourable for robot designing is its flexibility which allows the modification of design and structure in case of need. Moreover, this material is light in weight which facilitates easy and smooth movement of the robot. Lastly, it is possible to drill a hole or to insert a screw in plastic even after the completion of printing process by 3D printer. It is also essential to use the motor with appropriate power and dimensions. The robot may suffer from damage if the motor power exceeds the required power. Moreover, high power may prevent the robot from moving in appropriate direction. This robot was installed with the hobby motor 6.0 VDC because this motor has the appropriate size and power that allows easy fitting and operation of the robot. The new mechanical design of the four-legged linkage robot is aimed at light weight, robust, and flexible design with dynamic stability. Overall the aim is to improve speed with high stability of walking system. The system provides new features and phase offset between the legs of robot. The mechanical model of robot allows to produce smooth motion with rhythmic style (Kikuchi, Ota, & Hirose, 2003). The fast speed and motion of the robot are directly related to the overall weight of the robot. The four-legged spider robot designed here is developed by using composite materials. The composite materials are light weighted and highly durable. These materials are resistant to accidents such as an acid spill, fire accidents, and smash of the robot during motion (Rynkevic, Silva, & Marques, 2014).   

Figure 8:VDC Hobby motor

The difference in the type is linked with the difference in the usage. Due to the lightweight composite material-based body, the robot moves easily on application areas and face fewer physical barriers on the minimum motion levels (Mojdehi, Alitavoli, Darvizeh, Rajabi, & Larijani, 2011). The communication function of the robot is designed under the Bluetooth module that provides services of communication between the robot and the associated computer system. In the motion controlling process, the command is first transmitted through the Bluetooth services that are linked to the robots. The design of multi legged robots depends on balanced control and sensitive motion (Tolga Karakurt, 2015).

 In the previous work, the four-legged spider robots were designed with walking algorithms. In the present work, the fastest walking algorithms were developed for the hexapod system. Petri net algorithms are developed for the formulism of the coherent system with synchronization and direction analysis. The feasible system is designed for system modelling. The structure of Petri net algorithms for the four legged spider robots consists of five elements that are demonstrated by and these 

In the Petri net, the response is simulated under the system dynamics and input places are designed to activate the transition. The activated transition is fired and w (p,  t) token is connected to the transition. The weight between the transition and places is shown as a function of time and moment that is w(p, t) (Mojdehi, Alitavoli, Darvizeh, Rajabi, & Larijani, 2011). The mechanical components, control of the system, and design of the robot are improved in the model. The model designed here control the system based on four legs and have applications in the rescue operations. The motion of the system is related to the electronic structures and functions are done with a suitable receiver transmitter system (Karakurt, Durdu, & Dursun, 2015).

Challenges and limitations of Design spider robot

The size and shape of the robot legs are among the most crucial factors involved in this project. The legs must be designed in such a way so as to allow smooth walking of the robot. The dimensions selected for legs are tested during the sketching phase to observe their outcome and to make amendments in the dimensions if necessary. Additionally, the project involved complications regarding the motor dimensions and the connection between gears and shaft. It is very important for the motor to have a smaller size so that it can be easily placed in the robot’s body. Besides this, the power of the motor must be appropriate to operate the robot’s walking action. Finally, another crucial aspect in the walking robot is the dimension of the smallest linkage which must have appropriate size with respect to the robot’s body to facilitate its placement and smooth walking of the robot.

The motion of the robot is further subcategorized in various designs. The walking principle is based on the motion of all four legs and in case of damage of more than 3 legs, the robot face failure in motion. The IP camera only takes images of the location, but it cannot record video and audio therefore it is important to add a new feature of recording videos by using robots (Dwivedi, Sundaresan, & Perumal, 2013).

Timelines of Design spider robot

All the procedures involved in the project showed correspondence with the schedule included in the Gantt chart. However, the placement of motor in the robot was not done as per the schedule since the connection of gear and the robot legs involved some complications. Moreover, the part of the body attached to the motor was not formed appropriately because of inaccurate computations which called for remodeling of that body part to ensure the correct placement of motor in the robot and consequently, a friction-less movement of the robot.

The timeline of present work consists of different work processes with the time range. The timeline of the present work consists of literature review, problem characteristic, comprehensive study with the approach of design, proposed solution design, metric and dimension analysis, implementation of proposed design for four legged spider robot and then performance evaluation. The deliverable of the project is the construction of robots that move on the four legs. The deliverables required for the project are visual system for the robot that pass through the performance evaluations. The hazardous material is considered for the detection and process. It is easy to use interface for the controlling process of the robot by computer controller. The intelligent graphical user interface of computer for the robot highlight the operation process. The designing of GUI theory will help in developing the control interface. It provides display that is relevant to the information and operation. The programmed system will help in preventing the overloading and the operation for the entire robot sensor data through the relevant information. Before designing project program, it is important to measure the success factors regarding the operation and controlling process of robot. The success factors of the robot control are mainly affected by the effective and usable interface of robot.

Risk assessment of Design spider robot

The possible risk assessment is carried out to evaluate the possibility of failure of design before proposed method. The possible risk factors in the process are listed below,

1.      Risk of software testing during construction and maintenance.

2.      Software and computer system bugs that can cause irregularities to the robot and robot system.

3.      Because of time constraints, it is expected that deliverable may not be met.

Conclusion of Design spider robot

The formation of a walking robot is based on the concepts of mechanical engineering. Mechanical engineering involves the study of the designing, development and testing phases involved in mechanical designing. The concepts of sketching, theories, equations and Solid works related to mechanical engineering helped in the formation of an efficient design of the walking robot and helped in supporting the preceding parts of the study. Furthermore, the robot category having the structure designed for a specific purpose (such as walking in this case) is specified by the mechanical structure. Additionally, we cannot ignore the significance of the electrical part of the robot or the component that provides energy to the robot to move and walk after it has been assembled completely. More research can be conducted with respect to this design to bring improvements in the basic design of this robot. Since this robot is designed to walk, its improvement may involve facilitating the robot to walk forward, backward and sideways with enhanced speed and smoothness. These improvements may involve the incorporation of additional links and making changes in the design and use of more powerful motor to allow the robot to depict more efficiency while moving.

The robot designers are always inspired by the nature of development and designing of legged robots that mimic the walking style of insects over the rough and flat surfaces. In the present work, the walking method and behavior of four-legged insects are considered such as spider araneids diadematids. In the working process, the image processing techniques are developed, and experimental work was carried out to obtain optimal parameters of the legs of the spider robots. The positions of the defined points on the legs of the robot were recorded and then analyzed. The position of the recorded points was used as input to model and implementation of the model was related to the parameters such as angular acceleration, velocity, and angle of motion. The mechanical properties were allocated such as mass and moment of inertia at the central point of the robot model with the joint torque quantitates to produce motion of the spider robot on the traversed path. The quantitates can be further used for the control and selection of actuators in the novel robotic system. The whole system mimics the motion and walking style of spider and work efficiently even on the rough surfaces. 

Future work of Design spider robot

In the coming future, the structure of the robot can be improved in many ways. The main and basic variation can be carried out by improving the mechanical components. In the first stage, the components used in the robot can be improved against the crash, fall and inversion preventions. In the reversal situation, the software and hardware system can be improved. In the hardware system, the new possible feature is to introduce a new motor that enables the 360 degrees rotation while working in any location.  In the present case, the failure of more than 3 legs led to failure in the motion of the robot. The robot can be improved in the future by walking only rear legs. The computational model can be designed for the motion of the body and legs so the robot can run as humanoid robots that balance against the center of gravity of the robot. While working in the flat terrain the progress and motion of robot can be increased by replacing the legs with wheels. Adding new wheels for the flat terrains can increase the speed of motion of the robot over the flat surfaces. The wheels can provide high velocity in case of need instead of the legs of the robots. The improvement in the motion of a four-legged spider robot can be further carried out by changing the design of the robot and by changing mechanical and software processes. One of the important features of this robot is the defense mechanism that is installed in the motion system algorithm. The robot records all from the IP camera such as detection of human beings and animals, motion of individual bodies, and stationary conditions of all the objects. The recorded data is in the form of images from the IP camera. New algorithms are required to record the data and location in continuous processes such as video recording and audio recording. Replacing IP camera with the efficient system can improve the capability of recoding but it could result as the weight on the body and legs of the robot. The best alternative is to design a light-weighted video recorder. The light weighted video recorder will improve the efficiency of detection without troubling the speed of motion of the robot body.     

References of Design spider robot

Dwivedi, D., Sundaresan, Y. B., & Perumal, K. (2013). Low-cost MultiTerrainRescuing 4-Legged Bot Prototype. International Journal of Engineering and Technology, 05(02), 888-899.

Karakurt, T., Durdu, A., & Dursun, E. H. (2015). Petri-Net Based Control of Six Legged Spider Robot. Conference paper, 01(03), 01-10.

Kikuchi, F., Ota, Y., & Hirose, S. (2003). Basic performance experiments for jumping quadruped. Conference: Intelligent Robots and Systems, 04(02), 01-10.

Mojdehi, A. R., Alitavoli, M., Darvizeh, A., Rajabi, H., & Larijani, H. (2011). MODELING AND SIMULATION OF SPIDER’S WALKING. International Journal of Design & Nature and Ecodynamics, 06(02), 83-96.

Morita, K., & Ishihara, H. (2009). 4-Legged Mechanism of Realizing Dynamic Running. - Basic movement of prototype II with drive system that enables locomotion change. Robots, 01(02), 01-10.

Rynkevic, R., Silva, M. F., & Marques, M. (2014). Biomechanical Modeling and Simulation of Spider Crab - Inspiration for the Development of a Biomimetic Robot. Modeling and Simulation, 03(05), 01-10.

Santos, P. G., Garcia, E., & Estremera, J. (2018). Improving Walking-Robot Performances by Optimizing Leg Distribution. Retrieved from core.ac.uk: https://core.ac.uk/download/pdf/36015102.pdf

Shahriari, M. (2013). Design, Implementation and Control of a Hexapod Robot Using Reinforcement Learning Approach. Control of Robot, 02(01), 01-10.

Spenneberg, D., Strack, A., Hilljegerdes, J., Zschenker, H., Albrecht, M., Backhaus, T., & Kirchner, F. (2005). ARAMIES: A FOUR-LEGGED CLIMBING AND WALKING ROBOT. Robots, 01(02), 01-10.

Teli, S., Agarwal, R., Bagul, D., Badawane, P., & Bandre, R. (2019). Design and Fabrication of Multi Legged Robot. International Research Journal of Engineering and Technology, 06(03), 01-10.

Tolga Karakurt, A. D. (2015). Design of Six Legged Spider Robot and Evolving Walking Algorithms. International Journal of Machine Learning and Computing, 05(02), 96-102