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Majority of today's fixed-pitch, electric-power quadrotors have short flight endurance (< 1 hour) which greatly limits their applications. This paper presents a design methodology for the construction of a long-endurance quadrotor using variable-pitch rotors and a gasoline-engine. The methodology consists of three aspects. Firstly, the rotor blades and gasoline engine are selected as a pair, so that sufficient lift can be comfortably provided by the engine. Secondly, drivetrain and airframe are designed. Major challenges include airframe vibration minimization and power transmission from one engine to four rotors while keeping alternate rotors contra-rotating. Lastly, a PD controller is tuned to facilitate preliminary flight tests. The methodology has been verified by the construction and successful flight of our gasoline quadrotor prototype, which is designed to have a flight time of 2 to 3 hours and a maximum take-off weight of 10 kg.

An effective scheme to simulate low-speed, contact-rich manipulation tasks is to assume quasistatic physics and advance system states by solving linear complementarity problems (LCPs). However, the existing LCP-based quasistatic time-stepping scheme fails to simulate grasping-an essential motion primitive in manipulation-due to two drawbacks specific to quasistatic systems. Firstly, inputs to quasistatic systems are velocity commands instead of torques. This can lead to penetration, and thus an infeasible LCP, when two rigid bodies in contact are commanded to push against each other. Secondly, as multiple force solutions exist for a given velocity command, a grasping velocity command is not guaranteed to generate sufficient grasping forces. In this paper, we reformulate the quasistatic time-stepping scheme as an optimization problem with complementarity constraints and a quadratic objective. By minimizing the difference between actual and commanded velocities, linearized non-penetration constraints can always be satisfied. Moreover, undesirable solutions with insufficient normal forces can be removed by considering elasticity, which is modeled by comparing actual and commanded velocities. The resulting optimization problem is a mixed-integer quadratic program, which can be solved reasonably quickly for smallto-medium-sized systems. The effectiveness of the proposed reformulation is validated by simulation results of systems with different levels of complexity.

Recent developments of pure electric vehicles have shown that pure electric vehicles equipped with two-speed or multispeed gearbox possess higher energy efficiency by ensuring the drive motor operates at its peak performance range. This article presents the design, analysis, and control of a two-speed automatic mechanical transmission for pure electric vehicles. The shift actuator is based on a motor-controlled camshaft where a special geometric groove is machined, and the camshaft realizes the axial positions of the synchronizer sleeve for gear engaging, disengaging, and speed control of the drive motor. Based on the force analysis of shift process, the parameters of shift actuator and shift motor are designed. The drive motor's torque control strategy before shifting, speed governing control strategy before engaging, shift actuator's control strategy during gear engaging, and drive motor's torque recovery strategy after shift process are proposed and implemented with a prototype. To validate the performance of the two-speed gearbox, a test bed was developed based on dSPACE that emulates various operation conditions. The experimental results indicate that the shift process with the proposed shift actuator and control strategy could be accomplished within 1 s under various operation conditions, with shift smoothness up to passenger car standard.

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