Spherical rolling mechanisms (SRMs) exhibit a number of advantages with respect to wheeled and legged mechanisms. In fact if the SRM is combined with the ...
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ScienceDirect Procedia Computer Science 76 (2015) 296 – 301
2015 IEEE International Symposium on Robotics and Intelligent Sensors (IRIS 2015)
MODELLING AND INVESTIGATION ON BOUNCING MECHANISM OF A SPHERE ROBOT N. M. H. Norsahperi*, M. A. Abdullah, S. Ahmad, S. F. Toha and I. A. Mahmood Department of Mechatronics Engineering, Kulliyah of Engineering, International Islamic University Malaysia, Gombak 53100, Malaysia
Abstract Spherical rolling mechanisms (SRMs) exhibit a number of advantages with respect to wheeled and legged mechanisms. In fact if the SRM is combined with the power of bouncing mechanism, it will produce an exciting phenomena that can be contributed to applications such as security surveillance, search and rescue. There is not much research done in both fields, especially in the bouncing mechanism. In fact to the best of authors’ knowledge no of research has been done on integrating both mechanism to produce a spherical system that is capable of rolling and bouncing, which can produce a very significant mobile robot. Therefore, this research deals with the modeling and development of a bouncing spherical robot using computational intelligent technique, i.e. Particle Swarm Optimization technique (PSO). A 3D virtual prototype of a spherical robot was developed in Visual Nastran as a platform for input and out data acquisition. Different simulations environment have been created, such as the free fall bouncing, shooting up and projectile type of environment to investigate the bouncing profile affected by different forces. The data obtained were then used for system identification using PSO technique with mean square error (MSE) of 0.0004%. The transfer function representing the bouncing mechanism of the sphere robot was then obtained. Next, the prototype of the sphere robot with bouncing capability was developed. Open loop tests have been conducted and the results show that the hardware developed can produce the bouncing mechanism at its promising capability. Future works need to be conducted to re-visit the hardware, particularly on the body of the sphere robot such that maximum bouncing can be achieved. © by Elsevier B.V. by This is an open access article under the CC BY-NC-ND license © 2015 2015Published The Authors. Published Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the 2015 IEEE International Symposium on Robotics and Intelligent Peer-review under responsibility of organizing committee of the 2015 IEEE International Symposium on Robotics and Intelligent Sensors (IRIS 2015). Sensors (IRIS 2015) Keywords: Bouncing Ball; Particle Swarm Optimization; Spherical Robot
1. Introduction A sphere is a unique shaped object where set of all points in the three-dimensional space lying at the same radius distance from the center of sphere. The advantages of sphere are that all positions are stable and provide complete symmetry. Additionally, sphere mechanism inherits a soft, safe and friendly look without any sharp corners or protrusions. Countries with irregular natural landscape and climate such as Japan and Malaysia need this particular mechanism for discovery and rescue purposes. Uneven land geography and climate caused exploration and rescue activities faced with several hampers such as mountains and sloppy terrains. Thus, mechanism with the ability to bounce is introduced to overcome this constraint. This mechanism can bounce in various surfaces such as sloppy, flat, smooth and rough surfaces. Other than ability to pass through different types of surface, some places are dangerous and unhealthy environment such as hazardous air, landslides or place that is difficult to reach by human.
1877-0509 © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the 2015 IEEE International Symposium on Robotics and Intelligent Sensors (IRIS 2015) doi:10.1016/j.procs.2015.12.294
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(a)
(b)
(c)
Fig. 1. (a) Self-propelled bounce ball patent, (Maxim et al., 1994); (b) Hoping mobility robot design, (Dubowsky et al., 2008); (c) Jollbot3 used for exploration, (Armour, 2010).
There are many significant applications when bouncing capability is needed such as entertainment, exploration and rescue. Entertainment focuses on children use. Bouncing mechanism as Fig. 1 (a) is used for many entertainment purposes. The ball only can bounce randomly at low height, which is suitable for entertainment purpose. Exploration activities limitation can be overcame by bouncing robot. Some of the established exploration robots are wheeledbased robot. Wheel robots have limitation, in the sense that it cannot pass through some constraints such as rough terrain or ravine. Hence, bouncing mechanism in Fig.1 (b) based robot is needed to overcome this limitation. Natural phenomena and disaster like volcano, tornado, landslides and buildings collapse can be harmful to human. These are very dangerous place to go especially for rescue purpose. A low weight robot as illustrated in Fig. 1 (c) can assists human rescuers in the place such as building collapse where some locations are deep and narrow to reach. Table 1 summarized the design specifications and capabilities of some existing sphere robot. Table 1. Summarized of sphere robot specifications and capabilities Researcher
Mazim et al., 1993
Dubowsjy et, al. 2008 Rescue
Sugiyama & Hirai, 2009 Exploration
Armour, 2010
Shape Memory Alloy= 8 Units Polymer Gel Unstated Battery
Servomotor=6V
Purpose
Entertainment
Actuator
DC Motor
Dielectric Elastomer=35 units
Exploration & Rescue
Sensor Power Source
Unstated Battery
Sniffing Camera Battery, Fuel Cell
Capability
Bounce Randomly
Bouncing=0.4m
Crawling Jumping=0.16m
Rolling Bouncing=0.449m
Features
D=0.075m
D=0.1m M=0.1kg
D=0.04m M=0.003kg
D=0.58m M=0.763kg
Unstated Battery
Despite that bouncing mechanism has been suggested for many purposes including entertainment and other activities, there have been minimum research done on the bouncing mechanism and its system modelling. Bouncing is a significant scenario to be studied in system engineering, where it can be manipulated for a greater impact of implementation if it may function as intended. It is also an example of a highly nonlinear system, which is complicated to model by using physical modelling method. Therefore, the main aims of this research are to investigate the bouncing mechanism and later to perform modelling the sphere robot. 2. Experimental Setup 2.1. Overview The design of the sphere robot in project was basically based on a biologically inspired jumping and rolling robot, Jollbot by Armour (2010) together with some modifications to the original design. Specifically, the mechanism for bouncing was inspired by the working principle of the mechanism in Jollbot. The bouncing mechanism can be divided into two main parts which are energy storing mechanism and energy release mechanism. The energy storing mechanism was used to store the energy in the rings. After the mechanism stored the energy in the rings, the release mechanism was used in order to bounce the sphere robot at desired height. The concept of bounce can be visualized as in Fig. 2.
Fig. 2. Bouncing mechanism used in Jollbot (Armour, 2010).
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2.2. Design of Bouncing Mechanism
Fig. 3. Bouncing mechanism assembly.
2.3. Sphere Robot Design
Fig. 4. Sphere robot design.
2.4. Integrated Design
Fig. 5. Integrated design of sphere robot.
(a)
(b)
N.M.H. Norsahperi et al. / Procedia Computer Science 76 (2015) 296 – 301 Fig. 6. (a) Actual integrated sphere robot (b) Fabricated bouncing mechanism.
2.5. System Configuration Gearbox (Store Motor)
Gyro Sensor
Main Controller
Motor Driver Micro Metal Gear Motor (Release Motor)
Accelerometer Sensor Fig. 7. Circuit system design
3. Results and Discussion The following simulations were done in order to collect the data for the modelling process. Empirical data’s were collected from the 3D virtual prototype. For this purpose, MSc Virtual Nastran 4D Software was used. This activity was important as the aim is to ensure that the spherical robot will perform as the ball in the simulation. In this activity, the data was divided into three categories which are free fall, force exerted from below and different angle of projection. Then, the collected data were used for the system identification. From the conducted system identification, a transfer function was obtained and the open loop test was conducted to acquire the system responses. 3.1. Positive Y-axis Force
Fig. 8. Simulation of force required to jump using Nastran Fig. 8 above shows how the simulation was done. The ball will start on the ground before s force was exerted below the ball. In order to counter the weight of the ball, the minimum force required is 30 N. In this simulation, the ball was designed to have 3 kg of weight as the mechanism and other components will be installed in the sphere robot. As the weight of the ball is about 30 N, thus, the minimum force required was assumed to be 30 N. The data was collected and divided into force versus highest height and time required to reach the maximum height.
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3.2. System Identification for Force (Input) and Height (Output) Actual vs PSO Prediction 50 Actual PSO prediction
45 40 35
Magnitude
30 25 20 15 10 5 0
0.5
1
1.5
2
2.5 Frequency (Hz)
3
3.5
4
4.5
5
180
200
(a) Mean Square Error (MSE) 0.5 MSE = 0.00037727
0.4 0.3
Magnitude
0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5
20
40
60
80 100 120 Time (Samples)
140
160
(b)
(c) Fig. 9. (a) Predicted output vs PSO output (b) Mean square error (MSE) of PSO (c) Transfer function open loop test.
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The parameters obtained for transfer function is as follow,
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(1)
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The Fig. 9 (a) and (b) shows that PSO provides the best output with only 0.000377 mean square errors and tracking the actual plant approximately equivalent to zero. Then, the transfer function in Eq. (1) was tested in the open loop with step function as the input using the sphere robot developed. The system was stable with almost no overshoot and with an approximately 0.05s settling time. 4. Conclusion In conclusion, the transfer function that represents the bouncing mechanism has been successfully derived using PSO technique from where the data are acquired from the input-output acquisition of the virtual prototype of the 3D sphere model. The sphere robot with bouncing mechanism has been successfully developed and tested in open loop environment. The design of the sphere robot can be further improved and optimized for better system performance with a suitable controller implementation. Referances [1] Armour R. H. (2010). A Biological Inspired Jumping and Rolling Robot. United Kingdom: University of Bath. [2] Arduino Uno. (2014). In Arduino Uno Product. Retrieved from http://arduino.cc/en/Main/ArduinoBoardUno [3] Boston P., Dubowsky S., Kesner S. & Plante J. S., (2008). Hopping Mobility Concept for Search and Rescue Robots. Massachusetts: Massachusetts Institute of Technology. [4] Conn, Danbury, Garnavillo, Maxim J., Reyner M. F & Thompson C., (1993). United States Patent No. 5,297,981, Iowa: United States Patent. [5] Sphere, (2014). In Encyclopaedia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/559619/sphere [6] Toha S. F. (2014). Model Selection. Gombak: International Islamic University Malaysia. [7] Toha S. F. (2014). Model Validation. Gombak: International Islamic University Malaysia. [8] Toha S. F. (2014). Basic Concepts of Physical Modelling and System Identification. Gombak: International Islamic University Malaysia. [9] Yuuta S. & Shinichi H. (2004). Crawling and Jumping of Deformable Soft Robot. Sendai: IEEE.
