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The Essboard is a kind of unusual, portable, two-wheeled vehicle with a special structure and unique locomotion mode. The rider can drive the Essboard easily by twisting the two pedals using both feet. The device may inspire a new type of two-wheeled mobile robots; however, study on this special kind of mobile system is quite inadequate. In this article, we address the kinematics—the most fundamental issue—of an Essboard. The geometric model of the system is first established; then, the holonomic constraints on the two wheels and the holonomic equations are obtained. Finally, the nonholonomic constraints on the system are derived under the condition of pure rolling, and thus the accurate kinematics of the system are established for the first time. To verify the correctness and effectiveness of the established kinematics, a simulation using the virtual prototype technique is conducted, and to reveal its accuracy and advantages, a comparison with the previous model is made. A physical prototype of an Essboard-like robot is developed and employed as a platform to verify the theoretical models. The kinematics built and verified in this article are general and can therefore be applied to other similar monorail vehicles including bicycles and motorcycles.

The global competition of the market and the rapid development of robots drives the application of robots to become more and more extensive and diverse. For example, SCARA has been widely used in industries like the automotive and the electronic products. However, the traditional robot has a fixed configuration and can only be used in a specific working environment, which cannot meet the needs of modern industry for flexible production. An effective way, to meet this challenge, appears to be the development of reconfigurable robotic systems. Based on the work of predecessors and inspired by the need of flexible production and modular design idea, we developed a modular SCARA, designed according to a modular method and mainly consisting of three independent joint modules, in series. This paper briefly introduces the principle of modularization design, the design process of each module, the control system and the configuration changes of a modular SCARA. The experimental results show that modular SCARA, with different configurations, can be easily constructed to adapt to different working environments, by following a modular design method, which is an important evolution step in the field of SCARA.

With the rapid development of robotics technology, balance and motion control of specific unicycle and two-wheeled vehicles have become achievable, and wheeled self-balanced mobile robots can be developed. Essboard is a wheeled vehicle, having different instability from an ordinary two-wheeled vehicle because of its two wheels that are arranged at the front and rear side. However, there is still a lack of relevant research on its balance control, so at present, it cannot be developed into a self-balanced two-wheeled mobile robot. In order to solve this problem, in this paper, a design concept of developing the Essboard into a two-wheel self-balanced robot Essbot by decomposing its motion is proposed for the first time. Besides, we develop and fabricate the Essbot, and propose its balance and motion control methods. Furthermore, the correctness and effectiveness of the designed Essbot and the proposed balance and motion control methods are verified by virtual prototype technology. Finally, the influence of different control laws on the Essbot’s motion is studied for the first time. The research results in this paper represent significant progress in the field of wheeled self-balanced robot and Essboard, and this is the first realization of the development of Essboard into a new type of two-wheeled self-balanced mobile robot.

Considering the problem of large steering error caused by hysteresis on the passive wheel of the Essboard, a kinematic model based on coordinate transformation is proposed to improve its precision of the wheel effectively. Firstly, the holonomic constraint equation and nonholonomic constraint equation are established. The Newton iteration method is used to solve the geometric relationship between the pedal roll angle and the wheel steering angle. Then, as a verification, the virtual prototype technique(VPT) is used to obtain the measured steering angle data. Comparing with the solution of the kinematics, it is found that the average error is 0.3° and maximum error is 2.4°. After comparing with the other literature(the average error is 8.2° and the maximum error is 14.5°), it is found that the kinematic model proposed in this paper is correct and can be applied to model the motion of the Essboard. In general, this kinematic equation can be applied to the other single-track vehicles, such as motorcycle with two-wheel steering, bicycles, etc. and it has a wide application value.