This approach ensures that Spike has the widest possible stance for his size and makes sure Spike’s body is as compact as possible. Therefore, the legs themselves are identical front to back, but mirrored side-to-side, while the Leg Motor Box is mirrored both front-to-back and side-to-side. Note that since, the legs are all designed by default to bend their joints in the same direction (essentially all the legs are designed as “front legs”, as anatomically the joints in the front and back legs of a cheetah bend anti-directionally relative to one another). Now that we have one leg completely designed, we simply need to appropriately mirror the Leg Assembly appropriately to go in each of the four locations. Also, as the four outermost bearings that allow for hip motion were still exposed, I designed a smaller 3D-printed bearing cover to shield the bearings from any contaminants. Similar to the upper legs, Spike’s body is designed specifically for easy assembly, with all the features necessary to hold panels together cut during the waterjetting process when the panels are made. Now that Spike’s body is coming together, I decided to invest some time adding the box-joints and bolt-nut holes that will allow Spike to be easily assembled. Since these parts are designed to be either waterjet or CNC-milled, adding this through cut-out feature adds very little effort or cost. To remedy this, I designed a cutout four each Leg Motor Box pulley. I also noticed an additional clearance issue with the Leg Motor Box Assemblies the pulley of each assembly is conflicting with the Lower Main Plate. In the picture below, you can see Spike with all four legs for the first time – finally starting to look like something! This is because I plan to add these later to the exterior of Spike, and protect them with sheet metal panels, as I imagine I’ll spend quite a bit of time under the hood of Spike.
#Spike robotics drivers#
It’s also apparent that Spike’s doesn’t have much room left for the many stepper drivers and onboard electronics. At this point, I also found it worthwhile to add side plates to Spike’s center to help retain the battery compartment. As discussed in the prior log, all this involves thanks to the modular design is to mirror the Leg Motor Box Assemblies relative to the Leg Motor Box Assemblies relative to the other side (front-back), as the legs all bend in the same direction at the olecranon joint. Īll Four Legs and Continuing the Design of Spike’s Body:.Two More Legs and Some Body Design Michael G.
While the assembly is quite tight, after some adjustment, there are no conflicts between the six degrees of freedom in Spikes front or back legs.
#Spike robotics series#
The series of holes in the inner Leg Tensioning Plate allows the adjustment of tension in both of the timing belts. Since there won’t be accessibility to get an allen key in to screw a idler/tensioner into a tapped hole, I decided instead to use the waterjet to cut ¼” holes into the inner Leg Retention Plates.Īs the holes aren’t tapped, the design was changed to leverage shoulder bolts going all the way through the holes, through the inner race of the bearing, and then tightened on the end by a nut onto the shoulder bolt’s threads.Īs can seen below, one of the motor’s timing belts goes to one leg, while the other goes to the other leg. I decided to again turn to the step-wise tensioning method talked about in an earlier log, but had to approach it a little differently to last time given space constraints. Of course, when I actually order the timing belts, they will be close to the right size, but certainly won’t be tensioned perfectly. Notice how the only post-processing work necessary on this part is to drill a hole in the side of the aluminum to allow the bolt to pass through to actually clamp the motors in place.Īt this point I found the length of the AT-5 timing belts and mocked them up in the design. I then designed another flexure motor mounting plate to clamp the two motors in place.Īs per the standard in the design of Spike, we’re letting the machines doing the work and taking advantage of the manufacturing process of waterjet or CNC-machining. Accordingly, I adjusted the height of the Leg Retention panels and other side panels such that there was room for two of the stepper motors one-atop-another. The plan is to have the motors arranged one-atop-another to get them in the limited space in between the Leg Motor Boxes. Using this manufacturing process, it’s also possible to machine the bore and a key slot to transfer the torque from the planetary output shaft to the pulley.
It’s worth mentioning here that the plan is to waterjet the zero-backlash timing belt pulleys to reduce cost. The hip motors are 15:1 planetary gearbox Nema 23 stepper motors, that get actual power to the hips via a AT-5 timinb belt. As discussed in a prior log, the two hip motors are going to be placed in the dead-space between either side’s Leg Motor Box. At this point, Spike still needs power to his hips.
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