SLUGS UAV: A flexible and versatile hardware/software platform for guidance navigation and control research

Abstract

Abstract-This paper presents the Santa Cruz Low-Cost UAV GNC Subsystem (SLUGS) developed at the University of California Santa Cruz. It is a versatile and flexible autopilot capable of controlling a small unmanned system. It is tightly integrated with MATLAB/Simulink, and allows for a simple and easy transition from pure simulation to HIL simulation to flight code. The hardware's main processing units are two lowcost dsPIC33F DSCs, one handling sensor input and the other managing the navigation and control loops. The sensor DSC implements a complementary attitude and position filter. An interprocessor communication protocol delivers fused attitude and position estimates to the control DSC. The control DSC implements low-level platform stabilization using PID loops, and higher level waypoint following based on a line-of-sight guidance law. Data is logged and available for replay post flight on both the ground station software, and also within MATLAB/Simulink. The hardware was installed on a low-cost single engine electric RC aircraft, and has been demonstrated to be capable of sustained autonomous flight. Several estimation topologies have been tested and developed using the system. The SLUGS is general, and can be adapted to multiple autonomous platforms such as helicopters, quadrotors, twin engine aircraft, ground, and marine surface vehicles.

On the Tradeoff Between Electrical Power Consumption and Flight Performance in Fixed-Wing UAV Autopilots

“…The set-points to the control surfaces servos may be autonomously computed (on board) or relayed through a radio-control link from a Ground Control Station (GCS) [5,6]. The normal operation is to operate autonomously when the objective is just to move the flight surfaces to control the aircraft dynamics between waypoints, these being obtained through a radio link.…”

“…It does this in the former situation to reduce power consumption in the onboard radio equipment, as well as to release bandwidth in the radio channel for payload applications; and in the latter, to create alternative routes to handle or avoid unexpected disturbances or encounters in the nominal path. It is these kinds of autonomous autopilot control mode [4,5,7] that are considered in this paper.…”

“…Usually they include RF communications, navigation sensors and GPS connections. The autopilot hardware is based on devices usually made in CMOS technology, such as Digital Signal Processors (DSP) or Digital Signal Controllers (DSC) running at clock frequencies of tens of MHz [5,8] and so executing tens of millions of instructions per second (MIPS). The reduction of the clock frequency shrinks the autopilot power consumption, because of the strong power consumption dependence of CMOS devices to the switching frequency of the internal transistors.…”

Rapid Flight Control Prototyping - Steps toward cooperative mission-oriented capabilities

“…The generated code, that is called a firmware, is uploaded to the chip memory once and then enables the code execution at every time when the system is turned on. The SOC design approach that starts with pure Simulink [4] modeling, code generation and implementation on one of the most widely used microcontrollers (dsPIC) was recently applied for the design of SLUG autopilot [5], [6]. The benefits of the approach and the high performance of the entire system have been demonstrated in a number of successful flight experiments, see [7].…”

“…The SOC design approach that starts with pure Simulink [4] modeling, code generation and implementation on one of the most widely used microcontrollers (dsPIC) was recently applied for the design of SLUG autopilot [5], [6]. The benefits of the approach and the high performance of the entire system have been demonstrated in a number of successful flight experiments, see [7]. The system built on SOC approach is very capable and robust, however does not enable in-flight modifications of the onboard algorithms.…”