specifications.md

Technical Specifications

Physical Dimensions

Body Structure

Parameter	Value	Unit	Tolerance	Notes
Body Length	117.0	mm	±0.5	Distance between front and rear leg attachment points
Body Width	98.0	mm	±0.5	Distance between left and right leg attachment points
Default Height	80.0	mm	±2.0	Vertical distance from ground to body center
Height Range	20-95	mm	-	Adjustable operating range

Leg Kinematics

Parameter	Symbol	Value	Unit	Tolerance	Notes
Leg Segment Length	L₁	42.0	mm	±0.3	Upper leg (thigh) segment
Foot Segment Length	L₂	76.0	mm	±0.3	Lower leg (shank) segment
Total Leg Reach	R_max	118.0	mm	-	Maximum reach: L₁ + L₂
Leg Workspace Radius	R_ws	95.0	mm	-	Practical working radius

Coordinate System

Body-Fixed Frame (B):

• Origin: Body center of mass
• X-axis: Forward direction (positive forward)
• Y-axis: Lateral direction (positive left)
• Z-axis: Vertical direction (positive upward)

Leg Frame (L):

• Origin: Leg attachment point on body
• Y-axis: Forward/backward in leg plane
• Z-axis: Vertical in leg plane

Servo Specifications

MG996R Servo Parameters

Parameter	Value	Unit	Notes
Operating Voltage	4.8-7.2	V	Nominal: 5.0V
Stall Torque	10.0	kg·cm	At 5.0V, 0°
No-Load Speed	0.17	s/60°	At 5.0V
Operating Angle	0-180	deg	Mechanical range
Control Signal	0.5-2.5	ms	PWM pulse width (1.5ms = 90°)
PWM Frequency	50	Hz	Standard servo frequency
Resolution	~0.1	deg	Effective resolution
Backlash	<2.0	deg	Typical mechanical play

Servo Layout

Component	Servos	PWM Ports	Function
Front Left Leg	2	2, 3	Hip, Thigh
Front Right Leg	2	7, 8	Hip, Thigh
Rear Left Leg	2	0, 1	Hip, Thigh
Rear Right Leg	2	10, 11	Hip, Thigh
Head	3	4, 5, 6	Yaw, Pitch, Roll
Tail	1	9	Wag

Total: 12 servos

Servo Speed Limits

Component	Max Speed	Unit	Notes
Leg Servos	428	deg/s	Maximum safe speed for leg servos
Head Servos	300	deg/s	Maximum safe speed for head servos
Tail Servo	500	deg/s	Maximum safe speed for tail servo

Sensor Specifications

IMU (SH3001)

Parameter	Value	Unit	Notes
I2C Address	0x6F	-	7-bit address
Accelerometer Range	±2g, ±4g, ±8g, ±16g	g	Selectable
Gyroscope Range	±250, ±500, ±1000, ±2000	dps	Selectable
Resolution (2g range)	16384	LSB/g	1g = 16384 counts
Resolution (4g range)	8192	LSB/g	1g = 8192 counts
Sampling Rate	100-1000	Hz	Configurable
Noise Density (Accel)	0.4	mg/√Hz	Typical
Noise Density (Gyro)	0.03	dps/√Hz	Typical

Ultrasonic Sensor (HC-SR04)

Parameter	Value	Unit	Notes
Operating Voltage	5.0	V	DC
Detection Range	2-400	cm	Effective range
Accuracy	±3	mm	At 20°C
Beam Angle	15	deg	-3dB beamwidth
Response Time	<100	ms	Typical
Resolution	1	mm	Limited by timing

Touch Sensors

Parameter	Value	Unit	Notes
Type	Capacitive	-	Digital output
Operating Voltage	3.3	V	Logic level
Response Time	<10	ms	Typical
GPIO Pins	17, 27	-	Left, Right

RGB LED Strip (WS2812B)

Parameter	Value	Unit	Notes
LED Count	8-16	-	Configurable
Control Protocol	WS2812B	-	One-wire protocol
PWM Frequency	800	kHz	Data transmission
Color Depth	24-bit	bit	8-bit per channel
GPIO Pin	18	-	PWM-capable pin

Camera Module

Parameter	Value	Unit	Notes
Resolution	5.0	MP	2592×1944 max
Sensor Size	1/4"	inch	Optical format
Frame Rate	30	fps	At 1080p
Interface	CSI	-	Camera Serial Interface

Power System

Battery Specifications

Parameter	Value	Unit	Notes
Battery Type	18650 Li-ion	-	2× cells in series
Nominal Voltage	7.4	V	2× 3.7V
Capacity	3000	mAh	Per cell
Total Capacity	3000	mAh	Series configuration
Discharge Rate	2C	-	6A continuous

Power Consumption

Mode	Current	Power	Notes
Idle	500	mA	3.7 W
Walking	1.5	A	11.1 W
Peak	3.0	A	22.2 W
Runtime	~1.5	hours	Typical usage pattern

Power Distribution

Rail	Voltage	Current Limit	Components
Servo Rail	5.0	V	3.0 A
Logic Rail	3.3	V	500 mA
System Rail	5.0	V	1.0 A

Control System

PID Controller Parameters

Parameter	Symbol	Value	Unit	Notes
Proportional Gain	Kₚ	0.033	-	Roll/pitch balance
Integral Gain	Kᵢ	0.0	-	Disabled
Derivative Gain	Kd	0.0	-	Disabled

Control Law:

u(t) = Kₚ·e(t) + Kᵢ·∫e(τ)dτ + Kd·de(t)/dt

Where:

• u(t): Control output (servo offset in radians)
• e(t): Error signal (target_rpy - measured_rpy)
• Kₚ, Kᵢ, Kd: PID gains

Gait Parameters

Walking Gait

Parameter	Value	Unit	Notes
Cycle Sections	8	-	Complete gait cycle
Steps per Section	6	-	Interpolation steps
Step Height	20	mm	Leg lift height
Step Width	80	mm	Forward stride length
Center of Gravity Offset	-15	mm	Body balance point
Duty Factor	0.75	-	Contact time ratio

Trotting Gait

Parameter	Value	Unit	Notes
Cycle Sections	2	-	Diagonal pairs
Steps per Section	3	-	Interpolation steps
Step Height	20	mm	Leg lift height
Step Width	100	mm	Forward stride length
Center of Gravity Offset	-17	mm	Body balance point
Duty Factor	0.5	-	Contact time ratio

Kinematic Constraints

Joint Limits

Joint	Min Angle	Max Angle	Unit	Notes
Leg Hip	-90	+90	deg	Lateral rotation
Leg Thigh	-45	+135	deg	Forward/backward
Head Yaw	-90	+90	deg	Left/right rotation
Head Roll	-70	+70	deg	Lateral tilt
Head Pitch	-45	+30	deg	Up/down tilt

Workspace Constraints

Constraint	Value	Unit	Notes
Maximum Reach	118	mm	L₁ + L₂
Minimum Height	20	mm	Ground clearance
Maximum Height	95	mm	Extended leg height
Lateral Range	±49	mm	Half body width

Environmental Specifications

Parameter	Value	Unit	Notes
Operating Temperature	0-40	°C	Recommended range
Storage Temperature	-20-60	°C	Non-operating
Humidity	10-90	% RH	Non-condensing
Altitude	0-2000	m	Above sea level

Mechanical Tolerances

Component	Tolerance	Notes
Body Dimensions	±0.5 mm	Manufacturing tolerance
Leg Segments	±0.3 mm	Link length accuracy
Servo Positioning	±2.0 deg	Mechanical backlash
Assembly Alignment	±1.0 deg	Leg attachment angle

References

1. Craig, J. J. (2005). Introduction to Robotics: Mechanics and Control (3rd ed.). Pearson.
2. Siciliano, B., Sciavicco, L., Villani, L., & Oriolo, G. (2009). Robotics: Modelling, Planning and Control. Springer.
3. Spong, M. W., Hutchinson, S., & Vidyasagar, M. (2006). Robot Modeling and Control. Wiley.
4. MG996R Servo Datasheet. Tower Pro.
5. SH3001 IMU Datasheet. Shenzhen Hope Microelectronics.
6. HC-SR04 Ultrasonic Sensor Datasheet. ElecFreaks.