Ant

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A quadrupedal robot, based on the model proposed in High-Dimensional Continuous Control Using Generalized Advantage Estimation. Moving in three dimensions, it consists of a torso and four legs connected together, each leg consisting of two hinged connecting limbs, which are at the same time connected to the torso by hinges. It is necessary to coordinate the movement of the four legs in the target direction by applying moments to the drivers of the eight hinges.

Specific Action Space	Box(-1.0, 1.0, (8,), float64)
Specific Observation Shape	(40,)
Specific Observation High	inf
Specific Observation Low	-inf

Specific Action Space

Num	Action	Control Min	Control Max	Name (in corresponding XML file)	Joint/Site	Unit
0	torque applied on the rotor between the torso and front left hip	-1	1	hip_1 (front_left_leg)	hinge	torque (N m)
1	torque applied on the rotor between the front left two links	-1	1	angle_1 (front_left_leg)	hinge	torque (N m)
2	torque applied on the rotor between the torso and front right hip	-1	1	hip_2 (front_right_leg)	hinge	torque (N m)
3	torque applied on the rotor between the front right two links	-1	1	angle_2 (front_right_leg)	hinge	torque (N m)
4	torque applied on the rotor between the torso and back left hip	-1	1	hip_3 (back_leg)	hinge	torque (N m)
5	torque applied on the rotor between the back left two links	-1	1	angle_3 (back_leg)	hinge	torque (N m)
6	torque applied on the rotor between the torso and back right hip	-1	1	hip_4 (right_back_leg)	hinge	torque (N m)
7	torque applied on the rotor between the back right two links	-1	1	angle_4 (right_back_leg)	hinge	torque (N m)

Specific Observation Space

Size	Observation	Min	Max	Name (in corresponding XML file)	Joint/Site	Unit
3	accelerometer	-inf	inf	accelerometer	site	acceleration (m/s^2)
3	velocimeter	-inf	inf	velocimeter	site	velocity (m/s)
3	gyro	-inf	inf	gyro	site	anglular velocity (rad/s)
3	magnetometer	-inf	inf	magnetometer	site	magnetic flux (Wb)
1	angular velocity of angle between torso and front left link	-Inf	Inf	hip_1 (front_left_leg)	hinge	angle (rad)
1	angular velocity of the angle between front left links	-Inf	Inf	ankle_1 (front_left_leg)	hinge	angle (rad)
1	angular velocity of angle between torso and front right link	-Inf	Inf	hip_2 (front_right_leg)	hinge	angle (rad)
1	angular velocity of the angle between front right links	-Inf	Inf	ankle_2 (front_right_leg)	hinge	angle (rad)
1	angular velocity of angle between torso and back left link	-Inf	Inf	hip_3 (back_leg)	hinge	angle (rad)
1	angular velocity of the angle between back left links	-Inf	Inf	ankle_3 (back_leg)	hinge	angle (rad)
1	angular velocity of angle between torso and back right link	-Inf	Inf	hip_4 (right_back_leg)	hinge	angle (rad)
1	angular velocity of the angle between back right links	-Inf	Inf	ankle_4 (right_back_leg)	hinge	angle (rad)
1	z-coordinate of the torso (centre)	-Inf	Inf	torso	site	position (m)
3	xyz-coordinate angular velocity of the torso	-Inf	Inf	torso	site	angular velocity (rad/s)
2	sin() and cos() of angle between torso and first link on front left	-Inf	Inf	hip_1 (front_left_leg)	hinge	unitless
2	sin() and cos() of angle between torso and first link on front left	-Inf	Inf	ankle_1 (front_left_leg)	hinge	unitless
2	sin() and cos() of angle between torso and first link on front left	-Inf	Inf	hip_2 (front_right_leg)	hinge	unitless
2	sin() and cos() of angle between torso and first link on front left	-Inf	Inf	ankle_2 (front_right_leg)	hinge	unitless
2	sin() and cos() of angle between torso and first link on front left	-Inf	Inf	hip_3 (back_leg)	hinge	unitless
2	sin() and cos() of angle between torso and first link on front left	-Inf	Inf	ankle_3 (back_leg)	hinge	unitless
2	sin() and cos() of angle between torso and first link on front left	-Inf	Inf	hip_4 (right_back_leg)	hinge	unitless
2	sin() and cos() of angle between torso and first link on front left	-Inf	Inf	ankle_4 (right_back_leg)	hinge	unitless

Specific Starting Randomness

Scope	Range	Distribution
angle of hip_1	\([0.5\pi-0.1, 0.5\pi+0.1]\)	uniform
angle of ankle_1	\([0.5\pi-0.1, 0.5\pi+0.1]\)	uniform
angle of hip_2	\([0.5\pi-0.1, 0.5\pi+0.1]\)	uniform
angle of ankle_2	\([-0.5\pi-0.1, -0.5\pi+0.1]\)	uniform
angle of hip_3	\([0.5\pi-0.1, 0.5\pi+0.1]\)	uniform
angle of ankle_3	\([-0.5\pi-0.1, -0.5\pi+0.1]\)	uniform
angle of hip_4	\([0.5\pi-0.1, 0.5\pi+0.1]\)	uniform
angle of ankle_4	\([0.5\pi-0.1, 0.5\pi+0.1]\)	uniform

Specific Episode End

• When Ant falls headfirst, the current episode ends: Terminated = True.