Daisuke Nakazawa

Autonomous Flying Robots

This chapter contains a non-technical and general discussion about unmanned aerial vehicles (UAVs) and micro aerial vehicles (MAVs). This chapter presents some fundamental definitions related to UAVs and MAVs for clarification, and discusses the contents of this monograph. The goal of this chapter is to help the reader to become familiar with the contents of the monograph and understand what to expect from each chapter.

Autonomous Control of a Mini Quadrotor Vehicle Using LQG Controllers

This chapter describes the techniques of modeling and controller design of attitude for Quad-Rotor MAVs Compared with a single rotor or a contra-rotating propeller small helicopter, the advantages of Quad-Rotor MAVs are that: they have larger payloads, they are more powerful and can more easily handle turbulence such as wind and they are easier to design using a compact airframe. The research about autonomous control for Quad-Rotor MAVs is very active now. A key characteristic of Quad-Rotor MAVs is that all the degrees of freedom of the airframe are controlled by tuning the rotational speed of four motors. Moreover, because their internal controller calculates angular velocity feed back by using a gyro sensor, the nonlinearity of the airframe becomes weaker and a linear model is more appropriate. Therefore in this chapter, we introduce the technique of linear modeling and model based controller design for Quad-Rotor MAVs and the performance of the designed controller.

Development of Autonomous Quad-Tilt-Wing (QTW) Unmanned Aerial Vehicle: Design, Modeling, and Control

In this chapter, we propose an autonomous attitude control of a quad tilt wing-unmanned aerial vehicle (QTW-UAV). A QTW-UAV can achieve vertical takeoff and landing; further, hovering flight, which is characteristic of helicopters, and high cruising speeds, which are a characteristic of fixed-wing aircraft, can be achieved by changing the angle of the rotors and wings by a tilt mechanism. First, we construct an attitude model of the QTW-UAV by using the identification method. We then design the attitude control system with a Kalman filter-based linear quadratic integral (LQI) control method; the experiment results show that a model-based control design is very useful for the autonomous control of a QTW-UAV.

Fundamental Modeling and Control of Small and Miniature Unmanned Helicopters

In this chapter, the modeling and control system design of unmanned helicopters are introduced. Two types of unmanned helicopters exist today – a single-rotor helicopter and a coaxial-rotor helicopter. In general, small helicopters with weights from 1 to 50 kg use the single-rotor mechanism, while miniature helicopters with weights less than 500 g use the coaxial-rotor mechanism. In this chapter, small and miniature unmanned helicopters are discussed. First, their mathematical models are obtained as a transfer function or state space equation. Subsequently, the optimal control design for the control method for both small and miniature unmanned helicopters is introduced.

Mathematical Modeling and Nonlinear Control of VTOL Aerial Vehicles

In an effort to make autonomous flight behaviors available to mini and micro rotorcraft, an embedded and inexpensive autopilot was developed. In this chapter, we present the main steps for designing a nonlinear flight controller for mini rotorcraft Unmanned Aerial Vehicles (UAVs). The proposed control system is based on the nonlinear model of rotorcraft UAVs and uses the inner and outer-loop control scheme. It considers system’s nonlinearities and coupling and results in a practical controller that is easy to implement and to tune. The asymptotic stability of the complete closed-loop system was proven by exploiting the theories of systems in cascade. In addition to controller design and stability analysis, the chapter provides information about the air vehicle, sensors integration and real-time implementation of guidance, navigation and control algorithms. A mini quadrotor UAV, equipped with the embedded autopilot, has undergone an extensive program of flight tests, resulting in various flight behaviors under autonomous control from takeoff to landing. Experimental results that demonstrate the capabilities of our autonomous UAV are presented.

Guidance and Navigation Systems for Small Aerial Robots

As the capabilities of Unmanned Aerial Vehicles (UAVs) expand, increasing demands are being placed on the hardware and software that comprise their guidance and navigation systems. Guidance, navigation and control algorithms are the core of flight software of UAVs to successfully complete the assigned mission through autonomous flight. This chapter describes some guidance and navigation systems that we have designed and successfully applied to the autonomous flight of a mini rotorcraft UAV that weighs less than 0.7 kg. The real-time flight test results show that the vehicle can perform autonomous flight reliably in indoor and outdoor environments.

Vertical vibration analysis for elevator compensating sheave

Most elevators applied to tall buildings include compensating ropes to satisfy the balanced rope tension between the car and the counter weight. The compensating ropes receive tension by the compensating sheave, which is installed at the bottom space of the elevator shaft. The compensating sheave is only suspended by the compensating ropes, therefore, the sheave can move vertically while the car is traveling. This paper shows the elevator dynamic model to evaluate the vertical motion of the compensating sheave. Especially, behavior in emergency cases, such as brake activation and buffer strike, was investigated to evaluate the maximum upward motion of the sheave. The simulation results were validated by experiments and the most influenced factor for the sheave vertical motion was clarified.

Design and Implementation of Low-Cost Attitude Quaternion Sensor

In this chapter, the development of a low-cost attitude sensor is introduced. In the previous chapters, the control system design method of several UAVs/MAVs with rotary wings was shown, and several kinds of controllers were designed. The most important controller is the attitude controller because if attitude control is not achieved, any other control such as velocity and position controls cannot be achieved. For achieving attitude control, it is necessary to measure the attitude of UAV/MAV. Hence, we require an attitude sensor. However, conventional attitude sensors are somewhat expensive and heavy, and they cannot be used for the attitude control of small UAVs and MAVs. Therefore, the design of an attitude estimation algorithm by using low-cost sensors, accelerometers, gyro sensors, and magnetic sensor is introduced. Finally, a low-cost attitude sensor has been developed and evaluated by comparing it with a conventional high-accuracy sensor.

Elevator Rope Tension Analysis with Uneven Groove Wear of Sheave

Traction elevators are suspended by multiple ropes. Uneven sheave wears affect the rope tension during the elevator operation. If the tension condition reaches to the critical traction ratio, a rope slip occurs. As the rope slip also affects the rope tension, a tension calculation with rope slip is necessary to evaluate the relation between the groove wear and the rope tension. In this paper, a tension evaluation model is derived by including the rope slip behavior and then the influence of the rope tension due to the groove wear is evaluated.

Linearization and Identification of Helicopter Model for Hierarchical Control Design

This chapter presents an analytical modeling and model-based controller design for a small unmanned helicopter. Generally, it can be said that helicopter dynamics are nonlinear, with coupling of each axis. However, for low speed flights, i.e., speeds less than 5 m/s, the dynamics can be expressed by a set of linear equations of motion as a SISO (Single Input Single Output) system. The dynamics of the helicopter are divided into several components. We derive a model for each component from either the geometric relation or equation of motion. By combining all components, we derive two linear state equations that describe the helicopter’s lateral and longitudinal motion. The parameters of the model are decided by helicopter specs. Based on the derived models, we design A control system by using the linear quadratic integral (LQI). The validity of these approaches is then verified by flight tests.