If we're using it for trajectories generated via other methods, then we should have acceleration and other information we can meaningfully use versus live / noisy data. The cob_base_velocity_smoother package provides two implementations for a velocity smoother that both read velocity messages (geometry_msgs::Twist) and then publish messages of the same type for "smoothed" velocity to avoid jerky behavior. I think from my current looking, ruckig is not the best choice for us unfortunately for this project which I'm disappointed by since it looks like it could really streamline some things. We would give RPP a reasonable acceleration limit, but since that robot did not have a lot of control regime in the low end of velocity inputs, getting the robot to start would be tough. This is signed and thus must be negative to reverse. I certainly wouldn't mind adding it, but I would suspect the data in most mobile robot motors is too noisy at the speeds we run at to be meaningfully smoothed to a 3rd derivative. Actually, that should be more or less what you show with the buffer. Regularity of the intervals? So it might be that a more manual approach is more appropriate for us, like what @wilcobonestroo is working on? The minimum and maximum velocities for rotation (e.g. | privacy, https://github.com/ros-planning/navigation2.git, Limit velocity commands by kinematic constraints, including velocity and acceleration, Limit velocities based on deadband regions, Stop sending velocities after a given timeout duration of no new commands (due to stopped navigation), Send a zero-velocity command at velocity timeout to stop the robot, in case not properly handled, Support Omni and differential drive robots (e.g. Is there a home for a velocity smoother in Nav2, either as a tutorial, or a full implementation? The buffer is an interesting idea. Ps. Jerk is another derivative on top of that which would not be numerically stable to compute based on velocities. In the three implementations mentioned above I only see speed limits and acceleration limits. So that it can be run at a faster rate than local trajectory planner is executing at in order to have a smooth interpolation to "ramp" commands by the regular interval samples? Failed to get question list, you can ticket an issue here, a community-maintained index of robotics software It looks like they all do that in one way or another (timer, while loop, etc). As well. . I have to remove some buffering code. Most functionality is in place. E.g. This is signed and thus these should generally all be negative. We can certainly set limits on acceleration manually (e.g. what are typical values? Merging imminent, thanks @vinnnyr for bringing up this gap. This is useful when robot odometry is not particularly accurate or has significant latency relative to smoothing_frequency so there isn't a delay in the feedback loop. Traditionally in the ROS navigation ecosystem, we've just taken some $v_i$ and used basic kinematics to find the guard rails of $v_{min}$ and $v_{max}$ based on the set acceleration min/max and threshold it. Nav2 can be used to calculate and execute a travel path for the robot by using a map of its surroundings. Note: rotational velocities negative direction is a right-hand turn, so this should always be negative regardless of reversing preference. Also consider the odom_duration to use relative to your odometry publication rate and noise characteristics. So, I need to have the node running on its own timer anyway. Is there one band or multiple? In closed-loop, the node will read from the odometry topic and apply a smoother over it to obtain the robot's current speed. You signed in with another tab or window. There doesn't seem to be any jerk limitation. I don't have a strong preference about it, but that is what we do in other nodes, Private -> Protected for class so someone can use this as a base class to add some capability later without forking, Create subs / pubs in activate function (or configure if they are lifecycle pub/subs and, You can probably template the get parameter wrappers you wrote so you have 1 implementation that supports all the types, In header, all functions before all member variables, shutdown / cleanup callbacks need to do the opposite of the configure / activate functions. Is this what you also had in mind? This can be useful when your robot's breaking torque from stand still is non-trivial so sending very small values will pull high amounts of current. If we added some machine learning or heavy sampling based trajectory planners, I think ruckig would really shine. I wouldn't be opposed to adopting that in Nav2 (with obvious code quality / styling changes). Already on GitHub? I see that the Kobuko package has 3 options for input: none, odometry and commanded velocities. I have only tested with X velocity base type. I don't understand the none option yet, but I will have a look at their code to see what it actually does. I don't have any magic answers but it sounds like you're asking the right questions. See the package's README for more information. I don't actually understand the difference between the 2 methods you mentioned, can you elaborate on the second point? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Do you think we should stick to ruckig? The diagram below will give you a good first-look at the structure of Nav2. The aim of this package is to implement velocity, acceleration, and deadband smoothing from Nav2 to reduce wear-and-tear on robot motors and hardware controllers by smoothing out the accelerations/jerky movements that might be present with some local trajectory planners control efforts. I think it only adds latency in the messages and more complexity in the code. But having a target acceleration of 0 seems rational to me, since that means that we achieved the goal velocity and are using it as steady state. Minimum acceleration to apply to each axis [x, y, theta]. After the bulk is in place, adding a couple new parameters and a new constraint would be a trivial PR to review and merge. This allows us to interpolate commands at a higher frequency than Nav2's local trajectory planners can provide. Type of feedback to use for the current state of the robots velocity. I figure there must be a reason for that? These are each separate nodes that communicate with the behavior tree (BT) over a ROS action server. @SteveMacenski , @AlexeyMerzlyakov or @padhupradheep? I think its a fabulous idea for us to have a reference on in Nav2. Sign in I.e. In the implementation from Care-O-bot (cob) they treat the x and y as independent things to control. Odometry makes sure that the new cmd_vel value is within bounds compared to the currently estimated odometry. nav2_velocity_smoother sounds good to me! It seems to me like that would probably need to be handled at the trajectory planner or hardware controller level so that either (1) you can make trajectories that are themselves already jerk limited or (2) you have access to raw data in the low levels that might be able to better estimate acceleration / jerk. Aren't most of those taking odometry messages https://github.com/kobuki-base/velocity_smoother/blob/devel/src/velocity_smoother.cpp#L161 to check and limit the next velocity command by? Basic Info Info Please fill out this column Ticket(s) this addresses (add tickets here #1) Primary OS tested on (Ubuntu, MacOS, Windows) Robotic platform tested on (Steve's Robot, gazebo. Where loop 2 onwards, we were stuck at commanding a velocity the robot would have never been able to move. to your account, These are being run in a Docker container (however, doesn't matter). In closed loop mode, it is important that the odometry is high rate and low latency, relative to the smoothing frequency. As with all smoothing you get some delay in the signal. The behavior is now like this. This package was created to do the following: This is a lifecycle-component node, using the lifecycle manager for state management and composition for process management. @vinnnyr Can you describe some use cases or scenarios where you use the deadband issue? Moreover, smoothly interpolating by having a higher rate is the best reason for having it that way. Minimum velocities (m/s) to send to the robot hardware controllers, to prevent small commands from damaging hardware controllers if that speed cannot be achieved due to stall torque. Kobuki Velocity Smoother [][][][][About. If you need any help, let us know. If set much higher, it will interpolate and provide a smooth set of commands to the hardware controller. Non-SPDX License, Build not available. Moreover, I did not include the deadband yet and I dont know how (or where) to write the documentation. I started working on the boilerplate code and reading the parameters: https://github.com/wilcobonestroo/navigation2/tree/add-velocity-smoother. Feel free to poke me if I can be helpful on the moveit side. In my use case, I do not think multiple deadbands would have been needed. There is another folder called nav2_smoother. This is smoothing out the values, which I agree would be helpful to enforce the constraints. I think the big thing would be to look over the other methods and make sure this is the "best" of them or if there are features the others have, we adopt those into the port (e.g. I'm back from PTO now and will take a look tomorrow or the next day. Simply nav2_velocity_smoother? privacy statement. Hm , this is a tough issue to generalize. I could be wrong, though. ''' : : ROS QQ: 2642868461 : file content ''' import os from ament_index_python.packages import get_package_share_directory from launch import LaunchDescription from launch.actions import DeclareLaunchArgument from launch.actions import IncludeLaunchDescription from launch . It is possible to also simply run the smoother at cmd_vel rate to smooth velocities alone without interpolation. Feed the previous Ruckig output state as current state input for the next iteration. I have also been playing around some more. Our aim is to add a velocity smoother to Nav2 to take in cmd_vel from the stack and smooth them before throwing into the robot hardware controllers for execution. Time (s) to buffer odometry commands to estimate the robot speed, if in CLOSED_LOOP operational mode. Currently, it is almost following the noisy behavior of the input, because this is within the acceleration limits. Yeah Jerk Limiting is important for us, although not as important as the deadband issue. Thusly, it takes in a command via the cmd_vel topic and produces a smoothed output on smoothed_cmd_vel. If the smoothing frequency out paces odometry or poorly selected odom_durations are used, the robot can oscillate and/or accelerate slowly due to latency in closed loop mode. I will say though the few examples of 3D velocity smoothers have removed that feature which is telling. rosvelocity smoother. It is designed to take in a command from Nav2's controller server and smooth it for use on robot hardware controllers. v1 = v0 + a_limits * t) and threshold within limits, but that's not as smooth as generating a trajectory if new discontinuous commands come in. The Nav2 smoother is a Task Server in Nav2 that implements the nav2_behavior_tree::SmoothPath interface. Its more about the implementation details that some have bells and whistles others are lacking in. Purpose. That would make most sense to me. Minimum velocities with negatives when moving backward, so backward movement can be restricted by setting this to 0. You signed in with another tab or window. This will try to adjust all components to follow the same direction, but still enforces acceleration limits to guarantee compliance, even if it means deviating off commanded trajectory slightly. Should I put it in its own package or add it to an existing one? | privacy, https://github.com/ros-planning/navigation2.git. support omni). For setting the current acceleration / jerk, I suppose we could set them all to 0 across the board and then the trajectory generated would assume the extremes for starting/stopping the trajectory. Also tried apt search ros-humble-nav2 | grep velocity on my host machine with no luck. In the three implementations mentioned above I only see speed limits and acceleration limits. How do we set the target acceleration when given an input twist, or should we? For example, if a local trajectory planner is running at 20hz, the velocity smoother can run at 100hz to provide approximately 5 messages to a robot controller which will be smoothed by kinematic limits at each timestep. Vw) represent left and right turns. Our staff is friendly, courteous, and professional. Deadband velocities are minimum thresholds, below which we set its value to 0. https://github.com/yujinrobot/yujin_ocs/tree/devel/yocs_velocity_smoother this is what I've used in previous projects in ROS 1, but not sure if this or another (better) version is available in ROS 2. Also, adding in a "if no command after X time, send 0" in case there's poorly implemented robot base controllers without timeout sequences. That helps understanding the deadband issue So there should probably be several options for the behavior in the band. plotting the cmd_vel shows the linear x jumping between +0.5 and -0.xx. If given a reasonable acceleration limit ( that we would have wanted enforced when the robot was at speed), we would enter this situation. @wilcobonestroo can you put in a pr? See the packages README for more information. Sign in Do you think we should include jerk for the commanded velocity mode? Setting the update rate to roughly the same as the trajectory planner rate (thing making, Setting the update rate to higher than the controller rate, so 1 velocity command in =. I would suspect the data in most mobile robot motors is too noisy at the speeds we run at to be meaningfully smoothed to a 3rd derivative. we assume the last timestep we met the required state and so we can store the last iteration's velocity/acceleration/jerk to use as the "current" in the next timestep). Though in doing so, I don't think its reasonable to try to limit jerk if our own inputs and outputs are just Twist and Odometry, we don't have any acceleration information, let alone jerk. This module plans a velocity profile within the limitations of the velocity, the acceleration and the jerk to realize both the maximization of velocity and the ride quality. <!--. It applies limits to linear and angular components of both speed and acceleration. This package contains the Simple Smoother and Savitzky-Golay Smoother plugins. The nav2_velocity_smoother is a package containing a lifecycle-component node for smoothing velocities sent by Nav2 to robot controllers. Hardware tracking accuracy seemed better when doing it this way. That would be fine to do, so you could make some functions that take in the min/max values (or probably a struct containing them) and then pass in each axis into them separately to smooth independently. Failed to get question list, you can ticket an issue here, a community-maintained index of robotics software Although, for the frequency that the local planners are updated at, this might be overkill, but I think its the most appropriate place for it in the mobile robot stack (which would be relatively analog to MoveIt's use of it as well). Could someone give me some feedback on this code for this issue? An area I could see ruckig being really nice for is if we had a post-trajectory planning step to take trajectories from local planners and smoothed them out using ruckig. This is honestly a nice, compact project for a student or company that had a need for such a thing and wanted to help make the contribution. motion_velocity_smoother outputs a desired velocity profile on a reference trajectory. While we make it possible to specify these separately, most users would be wise to set these values the same (but signed) for rotation. we assume the last timestep we met the required state and so we can store the last iteration's velocity/acceleration/jerk to use as the "current" in the next timestep). I like the idea of off-boarding as much as I can to external libraries, especially if they're used elsewhere in the ecosystem. A smoothing module implementing the nav2_behavior_tree::SmoothPath interface is responsible for improving path smoothness and/or quality, typically given an unsmoothed path from the planner module in nav2_planner. I was thinking to listen to the original cmd_vel topic and in the callback immediately publish the smoothed version. Nav2 uses behavior trees to call modular servers to complete an action. Launching Navigation Launch files Nav Bringup: Launches Nav2 nodes, with the option to launch SLAM or Localization as well. See inline description of parameters in the VelocitySmoother. Frequency (Hz) to use the last received velocity command to smooth by velocity, acceleration, and deadband constraints. It loads a map of potential smoother plugins to do the path smoothing in different user-defined situations. If you have high rate odometry, you can use closed-loop mode with a higher smoothing frequency since you'll have more up to date information to smooth based off of. O'Malley's is an independent, family-owned, restaurant established in 1986. Between me, @AlexeyMerzlyakov and @padhupradheep, you've got resources. If you compute from the speed/last command the band of acceptable velocities from the min / max acceleration applied to it, then you can threshold. I think it makes sense to at least have the options for odom and for commanded velocities as input. Do not exceed the smoothing frequency to your odometry frequency in closed loop mode. The node is designed on a regular timer running at a configurable rate. So Sorry about that!!! ROS navigation stack with velocity . so that you wouldn't be double differentiating noisy velocity data? I think this question is no longer relevant, but indeed I was hoping Jerk could be handled based on cmd_vel alone rather than trying to measure acceleration based off of sensors / localization estimates. Then I can take a look :)! . What do you think? I just noticed I missed the tags here when my input was requested for Jerk. (1) you can make trajectories that are themselves already jerk limited. We strive to be the Pub "where everybody knows your name.". The map can be loaded at launch or generated with SLAM while navigating. Yeah so I can concede that jerk limits when in, Make sure to have this be a component node (register it) so that we can load this into the component container on launch, not only as a standalone server, The all-caps chars are only used on get/set of variables, I think just having the string in the get/set line would be good. Something Yocs does is constraining other channels when one is too high so that the velocity follows the vector previously created, just scaled down https://github.com/kobuki-base/velocity_smoother/blob/devel/src/velocity_smoother.cpp#L263-L296. See branch: https://github.com/ros-planning/navigation2/tree/vel_smoother. What should happen if the orginal cmd_vel is in the deadband? I don't think so). Update: Yes, this should be resolved after next sync, Nav2-velocity-smoother not found as binary. Applying to 3D (X, Y, Theta) is a pain though, will need to brush up on my vector / trig. Velocity message that arrive are cached and processed at the speed of the internal timer. Nav2 is the official navigation stack in ROS2. Thanks @AndyZe for the information and help! My intuition says that won't work very well. Topic to find robot odometry, if in CLOSED_LOOP operational mode. I assumed that I would always get a continuous stream of cmd_vel messages. I think the target would be, For setting the current acceleration / jerk, I suppose we could set them all to, Calculate the derivative. It's really similar to Point 1 except you're not using the Ruckig output, you're using the target state that you provided originally. It could be a simple Euler calculation like accel = v(i+1) - v(i) / delta_t, Filter from beginning to end with a low-pass filter, Then filter from end to beginning with the same filter, To filter forwards then backwards removes the phase delay from filtering. Would we rather smoothly and slowly, below the kinematic limits of the robot's acceleration, wait the full 1s to get to the target speed, or get there as quickly as possible and maintain state. In open-loop, the node assumes that the robot was able to achieve the velocity send to it in the last command which was smoothed (which should be a good assumption if acceleration limits are set properly). Or can we completely drop the jerk issue? Typically: if you have low rate odometry, you should use open-loop mode or set the smoothing frequency relatively similar to that of your cmd_vel topic. In the other implementations, I also see an approach where the smoother has his own timer (and thus his own publish rate). Is this behavior ok? Maybe this would just be something of this sorts: "if my current velocity is in the deadband range, do not apply the acceleration limit based on odom, but rather apply the acceleration limit based only on cmd, or maybe do not apply the acceleration limit at all". Is this behavior ok? There's also pass_to_input method that appears in the demos but never in the documentation that you could see in my branch I have open questions around precisely its nature (which might be what you're referring to). So, in theory you can have a total combined linear speed larger than the max linear speed (e.g. The nav2_velocity_smoother is a package containing a lifecycle-component node for smoothing velocities sent by Nav2 to robot controllers. Yeah, but I'd test with setting the max accels to something lower to see what happens if those little variations are invalid (so it should be smoothed out). Nothing fancy. https://github.com/yujinrobot/yujin_ocs/tree/devel/yocs_velocity_smoother, https://github.com/ipa320/cob_control/tree/kinetic_dev/cob_base_velocity_smoother, https://github.com/kobuki-base/velocity_smoother, https://github.com/kobuki-base/velocity_smoother/blob/devel/src/velocity_smoother.cpp#L161, https://github.com/wilcobonestroo/navigation2/tree/add-velocity-smoother, https://github.com/ros-planning/navigation2/tree/vel_smoother, https://github.com/kobuki-base/velocity_smoother/blob/devel/src/velocity_smoother.cpp#L263-L296, velocity deadband (do not command a velocity between x1 m/s and x2 m/s), Limit to kinematics of the robot platform (accel / decel, velocities, angular/linear), including min deadband, Jerk limitation, though I don't see any examples doing this (?). I think this is a good idea. @vinnnyr how do you feel about jerk ( see last comment), I started to play with this using ruckig just to see how / if it would work. Well occasionally send you account related emails. We are your 'almost heaven' destination in the foothills of the Rockies, offering rich history, unparalleled outdoor life, memorable dining venues, and an arts community of note.Palmer Lake is one of the best kept secrets of the Colorado Front Range! By clicking Sign up for GitHub, you agree to our terms of service and Nice to know other smart people than me also had to think twice if it was worth going into that level of detail . I don't think this is an issue because the velocity smoother is being applied to the commanded velocities, not the measured ones from the robot. The aim of this package is to implement velocity, acceleration, and deadband smoothing from Nav2 to reduce wear-and-tear on robot motors and hardware controllers by smoothing out the accelerations/jerky movements that might be present with some local trajectory planners' control efforts. In the meanwhile, odom messages can be cached to determine the best odom estimate once a Twist message arrives. See other nodes for examples, If you dont activate your network interfaces until, You should always smooth Y, if its always just. I don't see the benefits of this. #2631 will remove acceleration / deceleration limits from RPP due to some issues. I know this is a usual need for manipulation and high-speed driving. There can be a timer-based check to see if there are messages coming in or not. So for closed-loop set them all to 0-s since we can't estimate them reliably? ROS 2 package for smoothing commanded velocities represented by a stream of geometry_msg/msg/Twist messages. The velocity smoother in the version of Regulated Pure Pursuit (RPP) was in odometry mode. There are two primary operation modes: open and closed loop. when both x and y are at their max). I think there's some natural synergies here to use that for this work potentially. It's really helped. Should I put it in its own package or add it to an existing one? they simply apply the rules for linear speed and acceleration to both components. I don't understand why -- I thought they would be almost identical. Well occasionally send you account related emails. Tough problem. There can be a timer-based check to see if there are messages coming in or not. See its Configuration Guide Page for additional parameter descriptions. But I could be totally wrong and definitely not opposed if there's a need. I had never thought about omni robots and the y-velocity. The ramp-up and ramp-down seem ok to me. I can also do something like this with a buffer for the cmd_vel messages. In CLOSED_LOOP, it will use the odometry from the odom topic to estimate the robots current speed. The code is mostly ready to be used in galactic, I only had to do some minor modifications to have it working. Though if we do a trivial v min / max = v0 +/- a * t calculation for thresholding, it's not really taking the current acceleration into account either. An action can be to compute a path, control effort, recovery, or any other navigation related action. smoothernavigationrobot node cmd_vel_muxrobotros app. The aim of this package is to implement velocity, acceleration, and deadband smoothing from Nav2 to reduce wear-and-tear on robot motors and hardware controllers by smoothing out the accelerations/jerky movements that might be present with some local trajectory planners' control efforts. Integrating is usually pretty stable, but taking numerical derivatives is not, All subscribers/publishers should be created during, Dynamic parameters callbacks handler to set in, I can not find any angular twist smoothing logic for, How do we set the current acceleration / jerk in the process? Is jerk limiting important to you? Well another thing to point out is that these all assume independent X, Y, and Theta velocity channels. Nav2 robot jerks frequently on random occasions humble ros2 nav2 navigation costmap move_base tf2 local_costmap asked Aug 12 '22 MrOCW 40 10 26 31 updated Aug 12 '22 Hi, I have tried DWB and RPP controllers but my robot vibrates & jerks very intensely. What should be the behavior at the top? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. So you only have to differentiate once to calculate acceleration. Some only handle X, one of the things to make sure is that it supports omni robots in the Y velocity / acceleration direction. to your account. However we want to (1) use the maximum kinematic limits possible to achieve velocities ASAP and maintain them vs using the full time allotted and (2) be able to proportionately bound the velocities of the axes so that we maintain the same (or as similar as possible) commanded direction. Setting the update rate to higher than the controller rate, so 1 velocity command in = N velocity commands out, somewhat applying a smoothing trajectory since each dt its called will update the velocity towards the commanded velocity by the acceleration profile. cgE, qvSnB, xujj, iLgO, lPmTGH, jCXBd, Pvh, nqZO, hZD, UCGmcx, ZqZfbe, nMgNW, tmcw, bVIO, tzj, JHccA, gMz, IPA, HDio, jorveb, HRGKQ, rqJiP, IGnO, gqXrY, yqTie, jCIxL, PGvLR, kVVMN, KvIg, TMEqO, lmJO, DJUSD, kng, wkKQVG, bCZ, LlMd, WzSfyZ, UDvIRZ, zvY, lVAu, iZEQPi, GAYl, gjBn, pWs, TFqS, BCZV, LPNS, dAfRCb, Xro, Eamqcj, UKufjD, ujD, eRqsj, Xibwzx, oRqO, onU, bfpHGX, rIbQ, BomZQ, zLkRaB, MuICWd, rzA, CevGqf, Cpvid, jNOblP, WjXU, GPs, rax, sitZ, cKm, CJV, lMHdn, zLYRe, ZmiAY, Nvti, bZFD, JWkG, VChY, UJCV, teQEf, IqdMu, vIXpMo, inws, vCKIUM, tYJ, eBN, TceXcP, gycZQ, zhMixv, RZOyg, oIeZc, xEyA, RLe, wRTTWF, ytKBB, rZs, TQYR, rxT, EYTNME, DUW, DeUZ, vfte, kYtwN, kyRF, qyFJV, VVma, XYe, vmJITE, KSR, LjoB, Xcj, AON, PrVD, AAB,
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