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Found 8 results

  1. lr101095

    Sawyer Path Planning

    Just wanted to ask if anyone would be able to suggest a method of path planning for sawyer (both in application and in simulation). There is no collision avoidance as of yet and is not yet necessary for what i'm trying to achieve. i just wanted to be able to dictate the path of the robot between two points (initial end-effector location and desired location, including end-effector orientation). I know MoveIt does have a path planner but i'm not sure how to use it. To my understanding, MoveIt is able to plan a trajectory between two poses and execute the calculated trajectory, of course considering joint limits etc. I want to be able to determine a path just by inputting the xyz and normal of a point. For example, I want to be able to move the end-effector to a surface (such as a a table surface) and have the end-effector's z-axis parallel to the normal of surface. Assuming that the xyz (global frame) of the table point is known, i want to be able to control sawyer to move from an arbitrary start point and move to the desired location with the desired orientation. Because of what i need help with, can someone also provide an explanation for how inverse kinematics would work with sawyer? i know there is the IK Service example that involves ik_service_client and SolvePositionIK. But i dont really understand what is going on in that example nor what it does. Any help would be much appreciated. Cheers, Luke
  2. lr101095

    sawyer inverse kinematics

    trying to write a program that subscribes to the endpoint states of sawyer through rostopics. i've opted to subscribe to each individual endpoint_state value. my program is based around ik_service_client, hence why i decided to subscribe to the individual values. I have the following: sub_p1 = rospy.Subscriber("/robot/limb/right/endpoint_state/pose/position/x", String) sub_p2 = rospy.Subscriber("/robot/limb/right/endpoint_state/pose/position/y", String) sub_p3 = rospy.Subscriber("/robot/limb/right/endpoint_state/pose/position/z", String) sub_q1 = rospy.Subscriber("/robot/limb/right/endpoint_state/pose/orientation/x", String) sub_q2 = rospy.Subscriber("/robot/limb/right/endpoint_state/pose/orientation/y", String) sub_q3 = rospy.Subscriber("/robot/limb/right/endpoint_state/pose/orientation/z", String) sub_q0 = rospy.Subscriber("/robot/limb/right/endpoint_state/pose/orientation/w", String) poses = {'right': PoseStamped( header = hdr, pose = Pose( position = Point( x = sub_p1, y = sub_p2, z = sub_p3, ), orientation = Quaternion( x = sub_q1, y = sub_q2, z = sub_q3, w = sub_q0, ), ), ), } However, as a test, i print "poses" and i get the following output: pose: position: x: <rospy.topics.Subscriber object at 0x7fe9f9c31c50> y: <rospy.topics.Subscriber object at 0x7fe9f9c31d50> z: <rospy.topics.Subscriber object at 0x7fe9f9c31d90> orientation: x: <rospy.topics.Subscriber object at 0x7fe9f9bd7050> y: <rospy.topics.Subscriber object at 0x7fe9f9c31e10> z: <rospy.topics.Subscriber object at 0x7fe9f9bd7710> w: <rospy.topics.Subscriber object at 0x7fe9f9bd79d0>} How am i able to print/access the actual data so i have an output of actual numbers that i can then pass on to perform inverse kinematics? I'm not sure if i'm using the correct data type (i.e. String or otherwise) to pass on the values. any corrections, suggestions or solutions would be much appreciated. - Luke
  3. lr101095

    vibrating model

    While running the sawyer simulation in intera 5.2, i can see that the model is vibrating. Calling rostopic echo robot/limb/right/gravity_compensation_torques, you can see that there are changes being constantly made in actual_position, actual_velocity, actual_effort and gravity_only. I compared the same topic to the real robot, and i saw no changes in the output. Does anyone know why this happens in the simulation or how to resolve it?
  4. lr101095

    joint angles in simulation

    I was comparing the joint angles and joint limits in the simulation and the real robot. I dont think the correct joint angles have been integrated in the simulation. I understand that there may be some variance in the real robot, but i just wanted to make sure i wasn't observing something incorrect. I am trying to run a program, that was written for the real robot, in simulation. It works as expected with the real robot. But there are several discrepancies that i am coming across when running the simulation. One concern is that the joint limits do no match those of the real robot. Because of this, the robot in simulation isn't in the correct pose. For example, in simulation, joint 6 (wrist) has a range of -3.14 to 3.14. The real sawyer has a range of -4.714 to 4.709 in the same joint. I'm not sure if that has anything to do the simulation failing to run the program as expected, but I feel it may because the lack in "flexibility" in the robot in simulation isn't allowing the required pose to be achieved. In the program i'm trying to run, a joint angle of 3.373 is required in the joint 6. Consequently, due to the range provided in the simulation, the required pose in not achieved. it is worth noting that i've only observed this difference in range in joint 6, and i haven't, as of yet, checked to see if there are discrepancies in the other joints. If anyone has any advice regarding how to resolve this, or if there is an upcoming update that resolves this issue, please let me know.
  5. lr101095

    SolvePositionIK and Transformations

    Can someone please explain how SolvePositionIK works in terms of path planning? I want to know how to solve for a trajectory by inputting the point position (and maybe orientation) in order to achieve a desired pose related to the reference point. I'm using a kinect in simulation to scan the environment. So I want to be able to take a point from the camera frame and calculate the position in the global frame so that the transformation required for IK to solve for the pose cam be derived. Can anyone also suggest a way of achieving that? Thanks in advance - Luke
  6. lr101095

    vibrating model

    I'm currently running intera 5.2 on my PC and trying to run a sawyer simulation with a force/torque sensor on the end effector. I'm using rqt_plot to get the readings from the f/t sensor. but i'm getting unnecessary noise from the signal even when the sensor is not in contact with anything. (see first screenshot) When i put the f/t sensor to a surface in a static manner (end-effector put towards the surface and kept in contact), the signal is violently oscillating between a max force and 0. (see second screenshot) Zooming into the model of both sawyer and the f/t sensor, i can see that they are both vibrating a little. i can tell because the shadow is oscillating a little bit. I'm posting this question on this forum because i wanted to ask if there have been any changes in the simulation since 5.2.2 was released? i also wanted to ask if anyone was able to resolve this "error"?
  7. sgattman

    Sawyer CAD Model

    Hello, It would be very helpful to have a CAD model of Sawyer so that it is easier to understand the space requirements needed around the robot as we move into production with it. Is there a CAD model (or drawings) available for Sawyer that I would be able to get ahold of for this task? Thank you for your time.
  8. FJFranquiz

    Sawyer Physics-Based Simulation

    Hey there, We are wondering if there is a way to simulate the motions of the Sawyer robot on a physics engine before testing the actual robot; just like Gazebo for Baxter. (We are using Intera 5.1 on Ubuntu 14.04) Thank you for your time, ERAU Spacecraft Development Lab