spotmicro.GaitGenerator package

Submodules

spotmicro.GaitGenerator.Bezier module

class spotmicro.GaitGenerator.Bezier.BezierGait(dSref=[0.0, 0.0, 0.5, 0.5], dt=0.01, Tswing=0.2)

Bases: object

BernSteinPoly(t, k, point)

Calculate the point on the Berinstein Polynomial based on phase (0->1), point number (0-11), and the value of the control point itself

Parameters:

• t – phase
• k – point number
• point – point value

Returns:

Value through Bezier Curve

BezierSwing(phase, L, LateralFraction, clearance_height=0.04)

Calculates the step coordinates for the Bezier (swing) period

Parameters:

• phase – current trajectory phase
• L – step length
• LateralFraction – determines how lateral the movement is
• clearance_height – foot clearance height during swing phase

Returns:

X,Y,Z Foot Coordinates relative to unmodified body

Binomial(k)

Solves the binomial theorem given a Bezier point number relative to the total number of Bezier points.

Parameters:k – Bezier point number Returns:Binomial solution

CheckTouchDown()

Checks whether a reference leg touchdown has occured, and whether this warrants resetting the touchdown time

GenerateTrajectory(L, LateralFraction, YawRate, vel, T_bf_, T_bf_curr, clearance_height=0.06, penetration_depth=0.01, contacts=[0, 0, 0, 0], dt=None)

Calculates the step coordinates for each foot

Parameters:

• L – step length
• LateralFraction – determines how lateral the movement is
• YawRate – the desired body yaw rate
• vel – the desired step velocity
• clearance_height – foot clearance height during swing phase
• penetration_depth – foot penetration depth during stance phase
• contacts – array containing 1 for contact and 0 otherwise
• dt – the time step

Returns:

Foot Coordinates relative to unmodified body

GetFootStep(L, LateralFraction, YawRate, clearance_height, penetration_depth, Tstance, T_bf, index, key)

Calculates the step coordinates in either the Bezier or Sine portion of the trajectory depending on the retrieved phase

Parameters:

• phase – current trajectory phase
• L – step length
• LateralFraction – determines how lateral the movement is
• YawRate – the desired body yaw rate
• clearance_height – foot clearance height during swing phase
• penetration_depth – foot penetration depth during stance phase
• Tstance – the current user-specified stance period
• T_bf – default body-to-foot Vector
• index – the foot index in the container
• key – indicates which foot is being processed

Returns:

Foot Coordinates relative to unmodified body

GetPhase(index, Tstance, Tswing)

Retrieves the phase of an individual leg.

NOTE modification from original paper:

if ti < -Tswing:

ti += Tstride

This is to avoid a phase discontinuity if the user selects a Step Length and Velocity combination that causes Tstance > Tswing.

Parameters:

• index – the leg’s index, used to identify the required phase lag
• Tstance – the current user-specified stance period
• Tswing – the swing period (constant, class member)

Returns:

Leg Phase, and StanceSwing (bool) to indicate whether leg is in stance or swing mode

Get_ti(index, Tstride)

Retrieves the time index for the individual leg

Parameters:

• index – the leg’s index, used to identify the required phase lag
• Tstride – the total leg movement period (Tstance + Tswing)

Returns:

the leg’s time index

Increment(dt, Tstride)

Increments the Bezier gait generator’s internal clock (self.time)

Parameters:

• dt – the time step phase lag
• Tstride – the total leg movement period (Tstance + Tswing)

Returns:

the leg’s time index

SineStance(phase, L, LateralFraction, penetration_depth=0.0)

Calculates the step coordinates for the Sinusoidal stance period

Parameters:

• phase – current trajectory phase
• L – step length
• LateralFraction – determines how lateral the movement is
• penetration_depth – foot penetration depth during stance phase

Returns:

X,Y,Z Foot Coordinates relative to unmodified body

StanceStep(phase, L, LateralFraction, YawRate, penetration_depth, T_bf, key, index)

Calculates the step coordinates for the Sine (stance) period using a combination of forward and rotational step coordinates initially decomposed from user input of L, LateralFraction and YawRate

Parameters:

• phase – current trajectory phase
• L – step length
• LateralFraction – determines how lateral the movement is
• YawRate – the desired body yaw rate
• penetration_depth – foot penetration depth during stance phase
• T_bf – default body-to-foot Vector
• key – indicates which foot is being processed
• index – the foot index in the container

Returns:

Foot Coordinates relative to unmodified body

SwingStep(phase, L, LateralFraction, YawRate, clearance_height, T_bf, key, index)

Calculates the step coordinates for the Bezier (swing) period using a combination of forward and rotational step coordinates initially decomposed from user input of L, LateralFraction and YawRate

Parameters:

• phase – current trajectory phase
• L – step length
• LateralFraction – determines how lateral the movement is
• YawRate – the desired body yaw rate
• clearance_height – foot clearance height during swing phase
• T_bf – default body-to-foot Vector
• key – indicates which foot is being processed
• index – the foot index in the container

Returns:

Foot Coordinates relative to unmodified body

YawCircle(T_bf, index)

Calculates the required rotation of the trajectory plane

for yaw motion

Parameters:

• T_bf – default body-to-foot Vector
• index – the foot index in the container

Returns:

phi_arc, the plane rotation angle required for yaw motion

reset()

Resets the parameters of the Bezier Gait Generator

spotmicro.GaitGenerator.Raibert module

Module contents