8. Sensors
GPS LIDAR
Battery Voltage
Ring Laser Stereo Vision
Gyro & Linear
Accelerometers
Engine Temp Joint angles
& Speed & forces
Hydraulic
Pressure, Flow
& Temp
9. BigDog Sensors
Measurement
Type Location N
Quantity
Knee,
Linear Pot Joint displacements Hip (2), 16
Ankle
Load Cell Actuator, ankle force Legs 16
Current Sensor Servo valve current eBox 16
Proprioception
Stereo Vision Obstacles, Optic Flow Body 3
Ground Slope
LIDAR Human Tracking Body 1
Gyro
3 angular rates
3 linear accelerations
Body 6 Exteroception
Temperature Engine, Oil temperature Body 3
Flow Oil flow Body 4
Pressure Oil pressure Body 2 Homeostasis
Engine RPM
Governor Body 2
Battery voltage
Total 69
10. Onboard Computer
• PC104 stack
• Pentium CPU
• QNX real-time OS
• Code: C++
• Custom I/O interface boards
• Functions Performed:
– Control
– Sensing
– Data Collection
– Communications
– Electric Power Distribution
11. Software Architecture
HUMAN FOLLOWING 10Hz PLANNING 2Hz DATA LOGGING 200Hz
LIDAR
Position Terrain Map Laser Data
Object Tracking Long Term
30 Sec Data Log
Cost Map
Fault Log
Terrain Map 5k vars
Planned Path
Visual Odometry
Smoothed Path
POSE ESTIMATION 200Hz
IMU Visual Leg CONTROL 200Hz
Odometry Kinematics 802.11
GPS IMU Smoothed Path Joint Data
World Position, Orientation Engineering Interface
Steering Command
IK
Gait Control
TDLO
DEVICE DRIVERS 1kHz
Actuation Commands 900
MHz RF
IMU Joint Data
LIDAR GPS ACTUATION 1kHz Operator Interface
Position Servos Force Servos
12. Software Processes
Function: Control Servo Logging
Description: Main process. Joint control, Log engineering
Balances and read sensors, data for
steers robot, command performance
odometry, actuators, development
communicates engine control. and failure
with operator. analysis.
Update
200 Hz 1,000 Hz 200 Hz
Frequency:
13. Vest Operator
Control Unit (OCU)
Head Mounted
Display
900 Mhz
Antenna
HMD
Electronics
Steering
controller
OCU Computer
Battery
900 Mhz
Radio
14. Control Principles
Support - Bounce on
springy legs
Balance - Move legs
with symmetry to
achieve balance
Posture - Keep body
level using stance
legs
15. Control – BigDog
Net force
Maintain Body Posture & moment
• Control of body posture
through force control Hip torque
control
16. Control – BigDog
Net force
Maintain Body Posture & moment
• Control of body posture
through force control Hip torque
control
Maintain Ground Contact
• Force control through
compliant leg shock
Position
control
17. Control – BigDog
Maintain Body Posture
• Control of body posture
through force control
Maintain Ground Contact Lateral
• Force control through velocity
compliant leg shock
Maintain Lateral Balance
• Place feet to control body
lateral velocity
Stance leg motion predicts
lateral veloc. and accel. for New stance
swing leg placement legs
18. Additional Controls
• Estimate ground plane using history of
leg kinematic data and odometry
• Adjust posture to optimize leg strength
while maintaining reach on terrain
• Use traction control to avoid, detect and
recover from foot slips
• Move legs to avoid leg collisions
• Determine ego-motion using kinematic,
inertial and visual odometry
19. Trot Control Features
• Engine Power Control.
• Engine RPM regulated in response to actual
and predicted load.
• Ground steepness, ground roughness, and
lateral body velocity predict demand.
• Leg Collision Avoidance.
• Adjacent legs have overlapping workspace.
• Swing leg trajectories avoid hitting adjacent
stance legs.
20. Trot Control
• X – Closed loop. Speed error corrected
by x direction foot forces.
• Y – Lateral foot position chosen to offset
unwanted lateral body velocity.
• Z
• Roll Coupled Controller.
Corrections for height and
• Pitch Euler errors map to y and z
• Yaw direction foot forces.
21. LIDAR Leader Tracking
• Follow leader without direct driving and without GPS:
– Leader wears retro-reflective marker
– SICK LIDAR used to locate leader and generate steering signals
– BigDog follows at approximate fixed distance
