# Design and Modeling of a Parent Big STAR Robot Platform That Carries a Child RSTAR
## 1 Introduction  
Miniature crawling robots inspired by Nature have long been developed for search and rescue missions that require offroad crawling and climbing over diverse obstacles. Their small size, low weight and high navigability enable their deployment in large numbers to quickly inspect a large area. The many palm sized robots include Mini-Whegs [1], Dyna-RoACH [2], DASH [3], iSprawl [4], OctoRoACH [5], RHex [6], Sprawlita [7], TAYLRoACH [8], STAR [9, 10], 1 STAR [11] and Rising STAR [12]. At this size, the design of these robots requires a minimalistic approach and reconfigurable mechanics such as sprawling mechanisms, passively transformable wheel-legs, rolling-crawling mechanisms and four bar mechanisms [13, 14, 15, 16, 17, 18, 19, 20]. There are several reports of collaboration between robots for offroad tasks such as search and rescue. There are numerous advantages to using multirobot systems which include compensating for a malfunctioning robot, multirobot collaborative control, pioneer and surveyor type robots, multirobot exploration and coverage as well as facilitating wireless communication [21, 22, 23, 24, 25]. [PERSON] et al. suggested a framework for a fault tolerant multirobot system that works cooperatively to achieve a common goal [21]. [PERSON] et al. presented a collaborative human robot control for multirobot systems where a single operator simultaneously controls multiple robots [22]. [PERSON] and [PERSON] developed a framework for multirobot path planning which coordinates robot motion only when needed [23]. [PERSON] and [PERSON] developed a motion planning method for tethered robots to cover an unknown planar environment with obstacles [24]. [PERSON] et al. developed a networked robotic system for enhancing wireless communication capabilities which can be used in GPS-denied environments [25]. [PERSON] et al. considered fitting a large, wheeled robot with a long ramp to carry a smaller tracked robot [26]. They suggested that the robots could be fitted with wireless LAN (local area network) cameras and laser range finders for remote control. However, the combined performance of the robot pair was not presented in typical scenarios and no mechanical properties of the design were provided. [PERSON] et al. [27] discussed using a large wheeled robot which carries a smaller wheeled robot that can deploy a smaller legged robot. Their main focus was on verifying the communication signal strength between the three robots. Their analysis remained on the conceptual level. [PERSON] et al. analyzed the collaboration between a quadruped hybrid parent robot that can carry up to seven reconfigurable small module robots which can form a chain like a snake [28]. However, similar to the two previous works, they provide no actual demonstration of the system (child-robot) collaboration or any mechanical/kinematic or energy analysis. In previous publications [9; 10; 11; 12; 13], we presented the sprawl tuned family of robots (STAR, 1 STAR, RSTAR and FSTAR) which are fitted with a sprawling mechanism inspired by cockroaches [29; 30] allowing these robots to transform their dynamics between the lateral to the sagittal planes. The STAR and RSTAR robots exhibited excellent abilities in moving over varying terrains, granular surfaces and when traversing obstacles. The most recent in this series is the flying STAR (FSTAR) which is capable of both driving and flying [31]. In this work, we present a novel \"parent\" STAR robot (BSTAR up-scaled by a factor of 7:1 from the original STAR robot and 6:1 relative to RSTAR see Figures 1 and 2) and a previously developed \"child\" RSTAR robot [12], (see Figure 3). The BSTAR is fitted with an actuated tail enabling the RSTAR to be carried on the back of the BSTAR and easily deployed. This paper is organized as follows. We first present the mechanical design of the two robots and their interface in Section 2.