Software Requirements Drive System

3.2 Drive System

3.2.1 Objectives

• Reliable tank-steering for new mechanical design.
• Validate in simulation before hardware.
• Intuitive control via Xbox controller.

3.2.2 Functional Requirements

FR-2.1 Simulation & Testing

• FR-2.1.1 URDF/CAD loads in RViz/Gazebo.
• FR-2.1.2 Validate tank-drive logic in simulation prior to hardware.
• FR-2.1.3 Simulation Readiness Gate:
  • Scripted forward/turn/pivot sequences pass.
  • E-Stop ≤ 0.5 s (latched).
  • Watchdog: if no /drive/cmd_vel ≥ 0.2 s → zero + warning.
  • Apply small dead-zone + exponential response; ≤ 0.2 m/s starts/stops are smooth.

FR-2.2 Drive Control Logic

• FR-2.2.1 Independent left/right motor groups (tank steering).
• FR-2.2.2 HAL translates to PWM/CAN/sim back-ends.
• FR-2.2.3 Configurable response curves (linear/exponential).

FR-2.3 Controller Integration

• FR-2.3.1 Xbox controller as primary input.
• FR-2.3.2 Mapping: Left stick → left motors; Right stick → right motors.
• FR-2.3.3 On disconnect: immediate neutral; no last-value hold.
• FR-2.3.4 Mappings/sensitivity defined in drive.yaml.

FR-2.4 Safety & Reliability

• FR-2.4.1 E-Stop halts immediately; latched until ~/clear_estop.
• FR-2.4.2 Clamp power within motor limits.
• FR-2.4.3 Manual override mode for troubleshooting.
• FR-2.4.4 Watchdog zeroes when command gap ≥ 0.2 s.

3.4 Non-Functional Requirements

ID	Type	Requirement
NFR-2.1	Performance	Controller latency ≤ 1 s.
NFR-2.2	Reliability	Operate ≥ 2 hours without faults.
NFR-2.3	Usability	Complete a basic obstacle course after ≤ 20 minutes.
NFR-2.4	Testability	Sim tests verify forward motion, turning radius, pivot.

3.5 Verification Criteria

See table below.

Test	Condition	Pass Criteria
Straight-Line Motion	5 m @ 0.3 m/s	In odom: cross-track ≤ 0.25 m; heading error ≤ 5°.
Pivot in Place (±90°)	±90° @ ~30°/s (~0.52 rad/s)	Final heading within ±5°;
Constant-Speed Cruise	0.3 m/s for 10 s	Avg 0.27–0.33 m/s (t=1–9 s); no sample exceeds max speed.
Watchdog	Stop /drive/cmd_vel ≥ 0.2 s	Publishes zero + WARN.
E-Stop	Trigger HW or /system/estop	Immediate zero until ~/clear_estop.
Controller Disconnect	Unplug during motion	/drive/cmd_vel zero within ≤ 100 ms; no residual motion.

Pre/post test steps: flat surface, nominal tires, bag /drive/cmd_vel and /localization/odom_local; run each test twice and both must pass.