3D-Printed FPV Quadcopter: Build, Flight, and Failure Analysis

Modern UAV construction uses carbon fiber reinforced polymer for primary structures, with glass fiber providing electromagnetically transparent components for antenna housings. Autoclave curing provides superior performance but is costly; vacuum-bag oven curing offers an economical alternative. Hydrocarbon fuels provide approximately ten times the energy density of current battery technology, making them essential for long-endurance operations. Fuel cells represent promising intermediate technology that could bridge the gap between batteries and hydrocarbon fuels.

UGATU is developing intermetallic alloys combining titanium and aluminum for fifth and sixth generation aircraft applications, offering reduced weight while maintaining performance. The university developed friction welding technology for aerospace applications, already used in serial production. The university is establishing a Center of Competence for Unmanned Aerial Vehicles to consolidate competencies for UAV development including small aircraft, helicopters, and other unmanned systems. This ecosystem approach recognizes that successful UAV development requires integration of multiple capabilities from design to operation. The university is working toward consolidation into a larger system to achieve federal recognition and inclusion in the top 30 universities in Russia, competing with Samara and Kazan Federal Universities for federal funding.

Modern UAV construction employs multiple materials including carbon fiber composites, glass fiber composites, plywood, balsa wood, aluminum alloys, and PLA plastics. Carbon and glass fiber composites were selected for the D-box and fuselage due to high strength-to-weight ratio. The wet layer hand lamination process involves adding carbon fiber cloth layer by layer with resin. 3D printing enables production of complex shapes like winglets and connectors, while topological optimization reduces weight by redesigning internal structures. Ribs serve as transverse support systems securing shape, capturing loads, and reinforcing edges. This multi-material approach balances performance, manufacturability, and packaging constraints.

This segment presents two major UAV development approaches: (1) Integrated UAV system architecture enabling end-users to operate technology without deep aerodynamic knowledge. Key developments include integrated ESC and flight controller using integrated driver IC with high-speed MOSFET capability and MCU for motor control; custom motor development using N52 magnets with Halbach array configuration for optimized magnetic field distribution; propeller development using carbon fiber composite with 12-inch for VTOL and 18-inch for fixed-wing flight; GCS development with 10-inch touchscreen, antenna tracker for 360-degree coverage, and automatic UAV tracking. Manufacturing involves CAD design, CNC cutting, vacuum infusion, and assembly. (2) Fruit fiber composite material using dried gambas (prawn) fiber as primary reinforcement for UAV wing construction. The material offers advantages including lightweight properties, high strength-to-weight ratio, utilization of agricultural waste, and cost-effectiveness. Manufacturing process involves fiber extraction, cutting, grinding, blending, and screening for uniform distribution. Composite layup uses laser-cut polystyrene molds, epoxy and catalyst mixing, fiber layup, and curing. Testing follows ASTM standards: tensile testing (ASTM D638), impact testing (ASTM G256), and water immersion testing. The material shows improved plasticity and vibration damping compared to standard materials, though with reduced tensile strength.

Titanium offers superior strength-to-weight and high-temperature performance but is expensive and difficult to form. Super plastic forming diffusion bonding creates seamless titanium joints. Magnesium provides good strength-to-weight but requires protective coatings due to flammability. Composites achieve 15-25% weight savings and are used in 50% of Boeing 787. Ceramics provide unmatched high-temperature resistance for exhaust nozzles and heat shields.

To tune a PID controller from scratch, start by setting the integral and derivative values to zero, then gradually increase the proportional value until the system becomes unstable (oscillations grow), record this critical value, and set the proportional gain to approximately half of this instability point; next, incrementally increase the integral value to eliminate steady-state error and bring the actual value to the setpoint, adjusting based on observed reaction time; finally, add a small derivative value to minimize overshoot, but be cautious as excessive derivative can cause instability or adverse effects from system distortion. This systematic approach works for various applications, though PID values must be retuned for different process dynamics such as fast-acting systems (engines) versus slow-reacting systems (heating loops).

The Ziegler-Nichols Method 2 is an experimental technique for tuning PID controllers by first determining the ultimate gain (Ku) and ultimate period (Pu) through proportional-only control until sustained oscillations occur, then applying empirical formulas to calculate the proportional, integral, and derivative gains; this method requires the closed-loop system to have third-order dynamics or contain time delay to achieve oscillatory behavior, and while it provides a starting point for controller parameters, fine-tuning is typically necessary for optimal performance.

The PID tuner in Simulink Control Design automates the controller tuning process through systematic analysis: First, the tuner automatically linearizes the system to determine initial gain suggestions. Second, it displays both time-domain characteristics (step response tracking) and frequency-domain characteristics (gain margin, phase margin). Third, users can adjust sliders to trade-off performance metrics such as response speed versus stability margins. Fourth, the tuner supports proportional-only, PI, and full PID controllers. Fifth, the tuner can operate with Stateflow diagrams in the loop, linearizing the system based on the current state. This capability enables tuning of complex multi-mode control systems without simplifying the model.

This comprehensive section covers PID control theory through systematic testing. The proportional action (KP) moves the ball toward center but causes oscillation if too high. The derivative action (KD) reacts to speed (ΔX/ΔT) to stop the ball quickly. PD control combines both for stable stopping. The integral action (KI) accumulates error over time to eliminate residual offsets when KP and KD alone aren't sufficient. The complete PID equation Output = KP×Error + KI×∫Error dt + KD×(ΔX/ΔT) produces PWM signals for the servo. Properly tuned PID maintains the ball exactly centered regardless of initial displacement or speed.

Lithium batteries pose no greater fire risk than lead acid when properly installed. Three main chemistries exist: LCO (high energy density, short cycle life), NMC (high capacity/power, mid-range cycle life), and LFP (recommended for boats, high cycle life, low internal resistance, safest). Thermal runaway occurs when cells exceed safe temperatures due to damage, triggering chain reactions that generate heat. Different chemistries trigger thermal runaway at different temperatures: LCO ~150°C, NMC ~210°C, LFP ~270°C, Lead Acid ~400°C. FAA studies confirm LFP performs best in safety testing, with isolated cell failures not spreading to other cells. Battery Management Systems (BMS) protect lithium batteries by monitoring current, voltage, temperature, and balancing cells. Internal BMS integrates within the battery pack, while external BMS connects externally and can interface with multiple packs. Critical consideration is external communication capability rather than internal/external distinction—whether BMS can communicate with shore chargers, alternators, and other components to warn of impending shutdown and prevent dump loads.

Thermal runaway is an uncontrolled self-heating process where electrical energy from a short circuit causes heat, which releases oxygen from the cathode material. This oxygen then oxidizes other materials, releasing more heat in a positive feedback loop. LiFePO4 batteries are inherently safer because the oxygen in the phosphate structure is tightly bound and cannot be released. In contrast, NMC batteries can experience thermal runaway because their cathode releases oxygen when heated. Lithium batteries can be equipped with heating systems for cold weather operation, controlled by the BMS. The BMS prevents charging until the battery reaches minimum temperature (typically 2-5°C). The internal resistance of lithium batteries is strongly temperature-dependent - at low temperatures, the electrolyte has reduced ion mobility, causing internal resistance to increase significantly.

Electric vehicle fires are technically called 'thermal runaway.' Lithium-ion batteries consist of cells with anode and cathode electrodes immersed in conductive liquid. When cells break due to impact or rapid charging, a chemical reaction releases oxygen, CO2, toxic gases, and extreme heat (over 600°C). Unlike conventional fires, battery fires don't need external oxygen because the battery itself releases oxygen. All electric vehicles have built-in battery management systems that limit charge to approximately 95% rather than 100% to prevent overheating.

Battery pack design evolved from traditional cell-to-module-to-pack architectures toward integrated structural approaches. The Plaid model introduced dual-port cooling with both inlet and outlet on the same end, splitting the serpentine channel to ensure every cell receives both cold and hot water connections, creating uniform temperature distribution. The structural pack approach eliminates replaceable modules entirely, integrating cells directly into vehicle structure with laser-welded current collectors. Battery Management Systems (BMS) perform three critical functions: monitoring cell group voltages, measuring temperatures, and implementing balancing to equalize state-of-charge differences. Passive balancing uses resistors across high-SOC cells; active balancing transfers energy directly between cells. BMS architectures range from centralized 'spaghetti wire' configurations to distributed satellite configurations minimizing wire lengths and fault risks. Thermal management involves cooling plates, thermal interface materials, and foam materials serving dual purposes of accommodating cell expansion and providing vibration damping.

Thermal runaway in lithium-ion batteries occurs when a single cell failure triggers a chain reaction that spreads to neighboring cells, releasing flammable gases and generating extreme heat; in electric vehicles with thousands of cells, this creates rapid pressure buildup that activates safety vents, producing energetic jet flames, while water application can slow the runaway but leaves damaged cells prone to reignition due to compromised electrical connections.