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How to properly use MultibodyPlant::CalcGravityGeneralizedForces in pydrake?
How to merge two dictionaries in a single expression?How do I check if a list is empty?How do I check whether a file exists without exceptions?How can I safely create a nested directory?How to get the current time in PythonHow can I make a time delay in Python?How do I sort a dictionary by value?How to make a chain of function decorators?How to make a flat list out of list of listsHow do I list all files of a directory?
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
I am trying to create a simple gravity compensation controller for acrobot with the following code:
from pydrake.all import *
file_name = "acrobot.sdf" # from drake/multibody/benchmarks/acrobot/acrobot.sdf
plant = MultibodyPlant()
parser = Parser(plant=plant)
robot = parser.AddModelFromFile(file_name)
plant.AddForceElement(UniformGravityFieldElement([0.0, 0.0, -9.81]))
plant.Finalize()
nq = plant.num_positions()
nv = plant.num_velocities()
nx = nq + nv
nu = plant.num_actuators()
assert (nx, nu) == (4, 1)
plant_ctx = plant.CreateDefaultContext()
x_plant = plant.GetMutablePositionsAndVelocities(plant_ctx)
x_plant[:] = [0.1, 0.2,
0.3, 0.4]
tau_g = plant.CalcGravityGeneralizedForces(plant_ctx)
print tau_g
Unfortunately, tau_g is always zero.
It seems that the gravity vector is not applied to the robot.
How can this be fixed?
UPDATE:
Working C++ implementation:
systems::DiagramBuilder<double> builder;
MultibodyPlant<double>& plant = *builder.AddSystem<MultibodyPlant>(0.001);
Parser parser(&plant);
drake::multibody::ModelInstanceIndex robot_instance_index = parser.AddModelFromFile(full_name);
plant.AddForceElement<UniformGravityFieldElement>();
plant.Finalize();
systems::Simulator<double> simulator(plant);
// Simulator Context
VectorXd state = plant.GetPositionsAndVelocities(simulator.get_mutable_context());
state(0) = 0.5;
state(1) = 0.5;
plant.SetPositionsAndVelocities(&simulator.get_mutable_context(),state);
// prints -15.3096 -8.25483
std::cout << plant.CalcGravityGeneralizedForces(simulator.get_mutable_context()) << std::endl;
// Default Context
std::unique_ptr<Context<double>> context_ptr = plant.CreateDefaultContext();
auto context = context_ptr.get();
VectorXd state_2 = plant.GetPositionsAndVelocities(*context, robot_instance_index);
state_2(0) = 0.5;
state_2(1) = 0.5;
plant.SetPositionsAndVelocities(context, state_2);
std::cout << plant.CalcGravityGeneralizedForces(*context) << std::endl;
// prints -15.3096 -8.25483
python drake
asked Mar 27 at 9:22
asQueasQue
195 bronze badges
add a comment |
I am trying to create a simple gravity compensation controller for acrobot with the following code:
from pydrake.all import *
file_name = "acrobot.sdf" # from drake/multibody/benchmarks/acrobot/acrobot.sdf
plant = MultibodyPlant()
parser = Parser(plant=plant)
robot = parser.AddModelFromFile(file_name)
plant.AddForceElement(UniformGravityFieldElement([0.0, 0.0, -9.81]))
plant.Finalize()
nq = plant.num_positions()
nv = plant.num_velocities()
nx = nq + nv
nu = plant.num_actuators()
assert (nx, nu) == (4, 1)
plant_ctx = plant.CreateDefaultContext()
x_plant = plant.GetMutablePositionsAndVelocities(plant_ctx)
x_plant[:] = [0.1, 0.2,
0.3, 0.4]
tau_g = plant.CalcGravityGeneralizedForces(plant_ctx)
print tau_g
Unfortunately, tau_g is always zero.
It seems that the gravity vector is not applied to the robot.
How can this be fixed?
UPDATE:
Working C++ implementation:
systems::DiagramBuilder<double> builder;
MultibodyPlant<double>& plant = *builder.AddSystem<MultibodyPlant>(0.001);
Parser parser(&plant);
drake::multibody::ModelInstanceIndex robot_instance_index = parser.AddModelFromFile(full_name);
plant.AddForceElement<UniformGravityFieldElement>();
plant.Finalize();
systems::Simulator<double> simulator(plant);
// Simulator Context
VectorXd state = plant.GetPositionsAndVelocities(simulator.get_mutable_context());
state(0) = 0.5;
state(1) = 0.5;
plant.SetPositionsAndVelocities(&simulator.get_mutable_context(),state);
// prints -15.3096 -8.25483
std::cout << plant.CalcGravityGeneralizedForces(simulator.get_mutable_context()) << std::endl;
// Default Context
std::unique_ptr<Context<double>> context_ptr = plant.CreateDefaultContext();
auto context = context_ptr.get();
VectorXd state_2 = plant.GetPositionsAndVelocities(*context, robot_instance_index);
state_2(0) = 0.5;
state_2(1) = 0.5;
plant.SetPositionsAndVelocities(context, state_2);
std::cout << plant.CalcGravityGeneralizedForces(*context) << std::endl;
// prints -15.3096 -8.25483
python drake
asked Mar 27 at 9:22
asQueasQue
195 bronze badges
add a comment |
I am trying to create a simple gravity compensation controller for acrobot with the following code:
from pydrake.all import *
file_name = "acrobot.sdf" # from drake/multibody/benchmarks/acrobot/acrobot.sdf
plant = MultibodyPlant()
parser = Parser(plant=plant)
robot = parser.AddModelFromFile(file_name)
plant.AddForceElement(UniformGravityFieldElement([0.0, 0.0, -9.81]))
plant.Finalize()
nq = plant.num_positions()
nv = plant.num_velocities()
nx = nq + nv
nu = plant.num_actuators()
assert (nx, nu) == (4, 1)
plant_ctx = plant.CreateDefaultContext()
x_plant = plant.GetMutablePositionsAndVelocities(plant_ctx)
x_plant[:] = [0.1, 0.2,
0.3, 0.4]
tau_g = plant.CalcGravityGeneralizedForces(plant_ctx)
print tau_g
Unfortunately, tau_g is always zero.
It seems that the gravity vector is not applied to the robot.
How can this be fixed?
UPDATE:
Working C++ implementation:
systems::DiagramBuilder<double> builder;
MultibodyPlant<double>& plant = *builder.AddSystem<MultibodyPlant>(0.001);
Parser parser(&plant);
drake::multibody::ModelInstanceIndex robot_instance_index = parser.AddModelFromFile(full_name);
plant.AddForceElement<UniformGravityFieldElement>();
plant.Finalize();
systems::Simulator<double> simulator(plant);
// Simulator Context
VectorXd state = plant.GetPositionsAndVelocities(simulator.get_mutable_context());
state(0) = 0.5;
state(1) = 0.5;
plant.SetPositionsAndVelocities(&simulator.get_mutable_context(),state);
// prints -15.3096 -8.25483
std::cout << plant.CalcGravityGeneralizedForces(simulator.get_mutable_context()) << std::endl;
// Default Context
std::unique_ptr<Context<double>> context_ptr = plant.CreateDefaultContext();
auto context = context_ptr.get();
VectorXd state_2 = plant.GetPositionsAndVelocities(*context, robot_instance_index);
state_2(0) = 0.5;
state_2(1) = 0.5;
plant.SetPositionsAndVelocities(context, state_2);
std::cout << plant.CalcGravityGeneralizedForces(*context) << std::endl;
// prints -15.3096 -8.25483
python drake
asked Mar 27 at 9:22
asQueasQue
195 bronze badges
I am trying to create a simple gravity compensation controller for acrobot with the following code:
from pydrake.all import *
file_name = "acrobot.sdf" # from drake/multibody/benchmarks/acrobot/acrobot.sdf
plant = MultibodyPlant()
parser = Parser(plant=plant)
robot = parser.AddModelFromFile(file_name)
plant.AddForceElement(UniformGravityFieldElement([0.0, 0.0, -9.81]))
plant.Finalize()
nq = plant.num_positions()
nv = plant.num_velocities()
nx = nq + nv
nu = plant.num_actuators()
assert (nx, nu) == (4, 1)
plant_ctx = plant.CreateDefaultContext()
x_plant = plant.GetMutablePositionsAndVelocities(plant_ctx)
x_plant[:] = [0.1, 0.2,
0.3, 0.4]
tau_g = plant.CalcGravityGeneralizedForces(plant_ctx)
print tau_g
Unfortunately, tau_g is always zero.
It seems that the gravity vector is not applied to the robot.
How can this be fixed?
UPDATE:
Working C++ implementation:
systems::DiagramBuilder<double> builder;
MultibodyPlant<double>& plant = *builder.AddSystem<MultibodyPlant>(0.001);
Parser parser(&plant);
drake::multibody::ModelInstanceIndex robot_instance_index = parser.AddModelFromFile(full_name);
plant.AddForceElement<UniformGravityFieldElement>();
plant.Finalize();
systems::Simulator<double> simulator(plant);
// Simulator Context
VectorXd state = plant.GetPositionsAndVelocities(simulator.get_mutable_context());
state(0) = 0.5;
state(1) = 0.5;
plant.SetPositionsAndVelocities(&simulator.get_mutable_context(),state);
// prints -15.3096 -8.25483
std::cout << plant.CalcGravityGeneralizedForces(simulator.get_mutable_context()) << std::endl;
// Default Context
std::unique_ptr<Context<double>> context_ptr = plant.CreateDefaultContext();
auto context = context_ptr.get();
VectorXd state_2 = plant.GetPositionsAndVelocities(*context, robot_instance_index);
state_2(0) = 0.5;
state_2(1) = 0.5;
plant.SetPositionsAndVelocities(context, state_2);
std::cout << plant.CalcGravityGeneralizedForces(*context) << std::endl;
// prints -15.3096 -8.25483
python drake
python drake
asked Mar 27 at 9:22
asQueasQue
195 bronze badges
asked Mar 27 at 9:22
asQueasQue
195 bronze badges
edited Mar 27 at 13:17
asQue
asked Mar 27 at 9:22
asQueasQue
195 bronze badges
asked Mar 27 at 9:22
asQueasQue
195 bronze badges
asked Mar 27 at 9:22
asQueasQue
195 bronze badges
195 bronze badges
add a comment |
add a comment |
1 Answer
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I confirm that I see the same behavior, and don't see any obvious errors in your implementation.
I've opened https://github.com/RobotLocomotion/drake/issues/11051
answered Mar 27 at 12:15
Russ TedrakeRuss Tedrake
4412 silver badges5 bronze badges
add a comment |
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1 Answer
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1 Answer
1
active
oldest
votes
active
oldest
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active
oldest
votes
I confirm that I see the same behavior, and don't see any obvious errors in your implementation.
I've opened https://github.com/RobotLocomotion/drake/issues/11051
answered Mar 27 at 12:15
Russ TedrakeRuss Tedrake
4412 silver badges5 bronze badges
add a comment |
I confirm that I see the same behavior, and don't see any obvious errors in your implementation.
I've opened https://github.com/RobotLocomotion/drake/issues/11051
answered Mar 27 at 12:15
Russ TedrakeRuss Tedrake
4412 silver badges5 bronze badges
add a comment |
I confirm that I see the same behavior, and don't see any obvious errors in your implementation.
I've opened https://github.com/RobotLocomotion/drake/issues/11051
answered Mar 27 at 12:15
Russ TedrakeRuss Tedrake
4412 silver badges5 bronze badges
I confirm that I see the same behavior, and don't see any obvious errors in your implementation.
I've opened https://github.com/RobotLocomotion/drake/issues/11051
answered Mar 27 at 12:15
Russ TedrakeRuss Tedrake
4412 silver badges5 bronze badges
answered Mar 27 at 12:15
Russ TedrakeRuss Tedrake
4412 silver badges5 bronze badges
answered Mar 27 at 12:15
Russ TedrakeRuss Tedrake
4412 silver badges5 bronze badges
answered Mar 27 at 12:15
Russ TedrakeRuss Tedrake
4412 silver badges5 bronze badges
4412 silver badges5 bronze badges
add a comment |
add a comment |
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