Klann Linkage Optimizer
Posted by Ben and Wade Vagle
This simulator allows you to quickly check how changing the bar lengths of Klann's Mechanical Spider mechanism affect its foot-path, but remember, just because something looks good in a simulation doesn't necessarily mean it will work well when built - at least not without some tinkering.
This simulator allows you to quickly check how changing the bar lengths of Klann's Mechanical Spider mechanism affect its foot-path, but remember, just because something looks good in a simulation doesn't necessarily mean it will work well when built - at least not without some tinkering.
Below is the embedded simulator. You can also run the simulator on MIT's site where you can modify the Scratch code. A description of the algorithms used in this Klann linkage calculator is here.
Klann Ver 2's LEGO bar lengths - Klann's patented linkage can be found below
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After changing a bar's length, click somewhere other than a slider bar and then press the space bar to see the new linkage and foot-path, and use your keyboard's left/right arrows to rotate the crank. Note: the "HiFrame" and "LowFrame" variables are the distances from the frame connections to the center of the crank.
If you want to more finely tune Klann's bar lengths by 1/10th increments see the "10x" simulator further down.
If you want to more finely tune Klann's bar lengths by 1/10th increments see the "10x" simulator further down.
When building a simulated linkage in LEGO, remember to use beams with one more hole than the bar's length. For example, a bar of length 8 requires a LEGO beam with 9 holes, because when determining the length of LEGO beams, the first hole is always counted as zero.
Also, be sure to incorporate triangles in your robot's frame to increase its rigidity. You can find other ideas for creating strong, triangle-based frames in LEGO here.
Also, be sure to incorporate triangles in your robot's frame to increase its rigidity. You can find other ideas for creating strong, triangle-based frames in LEGO here.
LEGO-Friendly Configurations of Klann's Mechanical Spider
The following options resulted from playing with the simulator as opposed to running some optimization code, so there are likely better LEGO configurations of the Klann linkage waiting to be found.
First, here's Klann's standard version from his patent with Klann's linkage measurements scaled so that the crank's length equals 3, alongside the LEGO version 2 approximation. Note: in the simulator you can choose the linkage from Klann's patent by pressing "k", followed by the space bar.
First, here's Klann's standard version from his patent with Klann's linkage measurements scaled so that the crank's length equals 3, alongside the LEGO version 2 approximation. Note: in the simulator you can choose the linkage from Klann's patent by pressing "k", followed by the space bar.
Klann Linkage Design from his Patent, and a LEGO Approximation
Below are the foot-paths of both versions, as well as the speed of the feet when in contact with the ground.
Notice how Klann's horizontal foot-speed slows at both corners of the foot-path. The feet slow down when they first contact the ground, as well as when they lift, which causes Klann to come to a stop with each step. Perhaps Klann's speed and efficiency could be improved with the addition of some sort of foot that reduced these speed differences?
As can be seen in the following simulations of Klann and other mech's walking across the screen, Klann's feet skid when the robot is moved at a constant speed. If the robot were instead moved at the speed of the feet, then it would have a halting gait like that of the LEGO prototype further down.
As can be seen in the following simulations of Klann and other mech's walking across the screen, Klann's feet skid when the robot is moved at a constant speed. If the robot were instead moved at the speed of the feet, then it would have a halting gait like that of the LEGO prototype further down.
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This experiment shows how feet that slide or rotate can smooth Klann's speed differences, which can be a problem at faster speeds: |
The Speed of Klann Linkage Robots can be Smoothed with Feet that Slide or Rotate
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Also, when the ground height changes Klann's forward speed drops or reverses due to it's triangular-shaped foot-path. This is further explored in this walking tanks post.
If you play with Klann's simulator you will probably notice how some types of modifications result in predictable changes to Klann's foot-path. For example, Klann's step-height can be increased by moving the lower rockers toward the center:
Directions for making this modification to Klann Ver 3 can be found here.
Below are two LEGO approximations of one of Klann's high-step configurations. If you consider building either in LEGO, you may want to separate the front and rear legs by a 40 tooth gear so that the top leg joints don't collide. Separating the legs should also make for a more stable robot when climbing, but it will require 2 more crank/axle systems - one for the front legs, and one for the back legs.
Below are two LEGO approximations of one of Klann's high-step configurations. If you consider building either in LEGO, you may want to separate the front and rear legs by a 40 tooth gear so that the top leg joints don't collide. Separating the legs should also make for a more stable robot when climbing, but it will require 2 more crank/axle systems - one for the front legs, and one for the back legs.
Klann Linkage with a High-Step
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Klann Linkage with a High-Step (2)
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The above high-step options may tend to trip when the feet are lifted off the ground due to the sharp angle of the foot-path's lower right corner. Also, the foot looks like it will reverse direction and drag a bit while still on the ground, so it may not work that well if the feet don't slide or rotate.
Below is another higher-step option, with a more rounded foot-path. The short leg version has B7=10 like Klann ver 2, and the long leg version has B7=14. Note: long-leg Mindstorms versions may not turn that well on non-smooth surfaces due to the leverage of the longer legs plus the weight of the EV3 brick - the legs would bend sideways, and maybe by a lot. You can see an example of this in the video of Klann's Spider - Mindstorms Long Legs.
Below is another higher-step option, with a more rounded foot-path. The short leg version has B7=10 like Klann ver 2, and the long leg version has B7=14. Note: long-leg Mindstorms versions may not turn that well on non-smooth surfaces due to the leverage of the longer legs plus the weight of the EV3 brick - the legs would bend sideways, and maybe by a lot. You can see an example of this in the video of Klann's Spider - Mindstorms Long Legs.
Klann Linkage with a Rounded Foot-Path
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Klann Linkage with a Rounded Foot-Path + Longer Legs
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Below is a slightly higher-step option:
Klann Linkage with a High-Step (3)
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Klann Linkage with a High_Step (3) + Longer Legs
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There are likely many more LEGO-friendly versions that can be found with the simulator, especially if LEGO's bent bars are included in the search (lengths shown below).
Here are a few ideas for making a 29 degree knee bend that the above options have.
Here are a few ideas for making a 29 degree knee bend that the above options have.
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Triangle used by "Clawfoot Klann" below
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Below is a 2X version of the 4-4-7 triangle for making a longer version of Klann's legs (B7=14), and an example of implementing it in LEGO to the right. Note that a 15 hole beam is required for a leg section of length 14, because when determining the length of LEGO beams, the first hole is always counted as zero. Here the the instructions for building Klann with these longer legs. 
Triangle used by Long-Leg Klann
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Example LEGO beams for Long-Leg Klann
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Clawfoot Klann below uses the 5-8-12 triangle for the lower leg section - plus a claw to help it to get over obstacles. Other than the lower leg sections, it's the same build as the Long-Leg Klann
Clawfoot Klann's lower leg section
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Lengths of LEGO's bent beams
Below is the "10x" simulator where the bar lengths have been multiplied by 10 and so can be changed by 1/10th of the above LEGO optimizer. Note: in the simulator you can choose the linkage from Klann's patent by pressing "k", followed by the space bar.
UPDATE: MIT released Scratch 3.0 on Jan 1, 2019, which currently doesn't allow variables to be set above 100 with the slider bar, nor decimals, meaning the above odd-length bars have to be put in the simulator's code on MIT's site - for now at least.
After changing a bar's length, click somewhere other than a slider bar and then press the space bar to see the new linkage and foot-path, and use your keyboard's left/right arrows to rotate the crank.
UPDATE: MIT released Scratch 3.0 on Jan 1, 2019, which currently doesn't allow variables to be set above 100 with the slider bar, nor decimals, meaning the above odd-length bars have to be put in the simulator's code on MIT's site - for now at least.
After changing a bar's length, click somewhere other than a slider bar and then press the space bar to see the new linkage and foot-path, and use your keyboard's left/right arrows to rotate the crank.
Below is an even higher-step possibility, but it may not function well with the sharp angle at the top of the foot-path? Note that you would need to make a smaller angle for the legs (12 degrees vs. the above 29 degrees)
Klann Linkage with a Higher-Step
Below are a few more possibilities. Notice the leg angles.
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