Project
| # | Title | Team Members | TA | Documents | Sponsor |
|---|---|---|---|---|---|
| 4 | Scorpion-Lift Ant-Weight BattleBot |
Chen Meng Zisu Jiang Zixin Mao |
Zhuoer Zhang | design_document1.pdf other1.docx |
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| Team Members: Zixin Mao(zixinm2) Chen Meng(meng28) Problem Many small combat/arena robots fail not because they lack “power,” but because they lose mobility (treads derailing, wheels slipping), cannot recover after being flipped, and cannot reliably control an opponent’s posture. Tracked robots have better traction, but keeping treads aligned under aggressive turning and impacts is difficult. Lifter-style control bots can dominate positioning, but they often struggle with self-righting and maintaining stable contact with opponents. We want to build a tracked, scorpion-shaped control robot that can (1) keep traction and mobility under collisions, (2) self-right and resist flips, and (3) control an opponent using two lifting arms (“claws”) plus a tail-mounted stinger mechanism for pushing/hooking/jabbing/bracing, without using destructive spinning weapons. The goal is a robust platform that demonstrates strong mechanical design and custom high-current circuits (motor drive, actuator drive, and power monitoring), suitable for a senior design scope. Solution We will build a differential-drive tracked platform (left and right tread) with a low center of gravity and a wide stance. Inspired by tracked designs that use self-centering tread geometry to prevent belt derailment, we will incorporate a crowned-pulley/self-centering tread approach to improve reliability during turns and impacts. On top of the base, we add: Two front lifting arms (scorpion “claws”) use a linkage mechanism to get a mechanical advantage and lift opponents/self-right. A scorpion tail “stinger” that can be positioned to brace against the ground for self-righting/anti-tip stability and can also be used as a control weapon to jab/push/hook opponents to disrupt their posture and set up lifts. Custom circuit boards: High-current dual motor driver (external MOSFET H-bridges with gate-driver ICs) Tail actuator power stage (H-bridge or MOSFET stage + current sensing + thermal protection) Power distribution + sensing (battery monitoring, current measurement, fusing, kill switch) This system directly addresses the problem: tracks provide traction, crowned/self-centering geometry improves tread retention, lifter arms provide control and self-righting, and the tail stinger adds a controllable “third-point” brace plus an active control/attack mechanism. Subsystems Overview and Physical Design Subsystem 1—Tracked Mobility and Drive Electronics 1) Function: Provide high-traction motion, fast turning, and robust tread retention under impacts. 2) Mechanical Approach: Differential tracked drive: one motor per side. Tread retention strategy: incorporate a crowned pulley/self-centering profile to reduce derailment during turning and shock loads. Commercial track set (baseline): Pololu 30T Track Set – Black, item #3033 (sprockets + tracks). If size/torque needs change, we can swap to a different Pololu track set family (e.g., 22T variants). 3) Actuators/Sensors (Explicit Parts): Gearmotors (with encoders for closed-loop speed control): Pololu 100:1 Metal Gearmotor 37Dx73L mm 12V with 64 CPR encoder, item #4755 (or equivalent 100:1 encoder variant). Motor driver (custom PCB, circuit-level design): TI DRV8701 brushed DC H-bridge gate driver (uses external N-MOSFETs for high current). We will design the H-bridge with appropriately rated MOSFETs, gate resistors, a current shunt, and a protection layout (high-current routing, thermal design). Prototype/fallback option: The VNH5019-class integrated driver can be used for early bring-up, but the final deliverable targets a discrete MOSFET + gate-driver solution for circuit-level depth. Current/voltage sensing: TI INA219 current shunt/power monitor (I²C) for battery + load telemetry (or per-rail monitoring where needed). 4) Key Circuit Deliverables (What We Will Design and Build): Dual H-bridge power stage (2x DRV8701 + MOSFETs) (prototype fallback: VNH5019-class module) Current sense + current limiting strategy (sense resistor + DRV8701 sense amplifier use) Reverse polarity + fuse + TVS transient suppression 5V/3.3V regulation for logic and servos (as needed) Subsystem 2—Dual Lifting Arms (“Claws”) Mechanism 1) Function: Lift/tilt opponents, perform self-righting, and stabilize the robot during control maneuvers. 2) Mechanical Approach: Two symmetric front arms shaped like scorpion claws. Linkage-based lifter (4-bar or similar) to amplify torque and keep the lifting motion controlled. 3) Components (Explicit Parts): High-torque metal gear servos (example): DS3218 digital servo (~20 kg·cm class)—one per arm, or one actuator with a shared linkage if weight/space demands. Arm position feedback (optional): potentiometer or magnetic encoder (e.g., AS5600) for closed-loop arm control beyond servo internal control. 4) Circuit and Interface Servo power rail design (separate buck regulator, bulk capacitance, brownout prevention) PWM generation from the MCU; optional current monitoring for stall detection Subsystem 3—Scorpion Tail “Stinger” and Driver Stage 1) Function: Provide a controllable tail mechanism that supports (1) self-righting, (2) anti-tip bracing while lifting, and (3) active control/attack against other robots via jabbing, pushing, and hooking. 2) Mechanical Approach: The tail is a rigid arm mounted at the rear/top of the chassis with 1–2 DOF: Pitch joint to raise/lower the tail (primary DOF). (Optional) small yaw adjustment to place the stinger left/right if needed. Tail tip “stinger” end-effector (replaceable modules): Jab/Pusher Tip: a rounded or wedge-shaped tip to shove and unbalance opponents without snagging. Hook Tip: a curved hook profile to catch on opponent edges (weapon guards, chassis lips, or external features) and pull/rotate them into the lifter arms. Brake/Brace Foot: high-friction pad to press into the ground for stability and self-righting. Operating modes: Self-righting push: the tail presses into the floor to lever the chassis upright. Anti-tip brace: as the front arms lift, the tail pushes down to prevent a backflip and stabilize the chassis. Jab/Poke: quick tail motion to disrupt opponent alignment and create an opening for the front claws. Hook-and-control: tail hooks and pulls to rotate the opponent or drag them into a favorable position. 3) Actuators/Sensors (Explicit Parts): Tail pitch actuator (choose one of the following implementation paths): Path A (simpler, lighter): high-torque servo (example: DS3218) for tail pitch joint. Path B (more force and controllable): compact DC gearmotor + lead screw (custom linear actuator) driving tail pitch via a crank linkage. Tail contact/force sensing (optional but recommended for protection and testing): Force-sensitive resistor (FSR) under the brace foot or a small load cell in the tail linkage to estimate applied downforce. Tail joint endstop sensing: limit switch or Hall sensor to prevent over-travel. 4) Power Electronics (Custom, Circuit-Level Design) If servo-based: a dedicated servo power rail with a buck regulator and bulk capacitance; monitor servo rail voltage sag. If DC motor/linear actuator-based: dedicated tail actuator driver PCB, including: H-bridge motor driver (gate driver + MOSFETs, or a motor-driver IC) Flyback/transient protection Current sensing (shunt + amplifier or INA219 channel) to detect stall and enforce safe limits Thermal monitoring near power devices and firmware cutback Subsystem 4—Wireless Control and Main Controller 1) Function: Reliable teleoperation, safety failsafe, and sensor telemetry. 2) Controller (Explicit Parts): ESP32-WROOM-32E-N4 module as the main MCU (Wi-Fi/BLE for control + telemetry). 3) Features: Wireless control (BLE gamepad or Wi-Fi UDP) Failsafe: if command packets stop for >500 ms (heartbeat) → motors stop, tail relaxes to safe position, arms relax to safe position Telemetry: battery voltage/current, motor currents, temperatures Subsystem 5—Power, Safety, and Compliance 1) Function: Safe high-current operation and course-lab compliance. 2) Planned Safety Hardware Physical kill switch / removable arming plug Main fuse sized for worst-case current + wiring limits Separate “logic” and “power” rails with filtering LiPo-safe practices: voltage cutoff, charging in approved bags/areas, current limiting for high-current loads Physical Design—3D Modeling and Fabrication 1) Modeling Software We will use Autodesk Fusion 360 for the entire mechanical design. 2) Material Since this is a combat robot, material properties are a primary design constraint. We will first consider PLA, PETG, and ABS materials (TBD). 3) Weight Management and Distribution General Weight Budgeting (Depending): Electronics & Motors: ~45% Battery: ~15% Mechanical Frame & 3D Prints: ~30% Fasteners & Tracks: ~10% Criterion for Success All goals below are clearly testable: 1. Mobility/Traction Maintain continuous drive for ≥ 10 minutes on a flat surface (no thermal shutdown). Reach ≥ 1.0 m/s straight-line speed on the lab floor with the full system powered. Execute 10 consecutive aggressive turns (full differential turning) without tread derailment. 2. Lifting Arms Lift a 0.5 kg test block by ≥ 30 mm within 3 seconds, repeated for 10 cycles without mechanical failure. Self-righting: from upside-down, return to upright in ≤ 5 seconds using the arms and tail pose in 3 out of 3 trials. 3. Tail “Stinger” (Stability and Attack/Control) Bracing downforce: when deployed in brace mode, the tail applies ≥ 30 N downward force on a scale (measured at the stinger foot) and holds for ≥ 30 seconds without actuator overheating or mechanical slip. Deployment speed: tail transitions from “stowed” to “bracing” position in ≤ 1.0 second, repeated 10 cycles. Anti-tip effectiveness: during a lift of the 0.5 kg test block, the robot does not tip past a defined angle threshold (e.g., < 45°) in 3 out of 3 trials. Jab/Pusher effectiveness: using the jab/pusher tip, the tail can push a 1.0 kg surrogate block on the lab floor by ≥ 20 cm within 2 seconds (repeatable in 3/3 trials). Hook-and-control: using the hook tip, the tail can latch onto a standardized pull point (e.g., a metal ring/edge on a test fixture) and pull a 0.5 kg load by ≥ 10 cm (repeatable in 3/3 trials). 4. Control and Safety Wireless control range ≥ 10 m line-of-sight with < 150 ms command latency. Failsafe stops the drive and disables high-force actions within ≤ 300 ms of signal loss (verified by logging + stopwatch/LED indicator). 5. Circuit-Level Design Validation The custom motor driver and tail actuator PCB operate at the target battery voltage and demonstrate: Current sensing accuracy within ±10% (bench compared to multimeter/shunt) No overcurrent damage during stall tests (protected shutdown triggers as designed) |
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