When designing anything the materials are always important. It is necessary to never get caught in fads or personal preferences. There is always an optimal solution that few ever reach because they don't appreciate this rule.
The prototype of our Jerry home robot has a wooden gripper. This was done in the interest of cost and speed of prototyping. Jerry as a whole is made almost entirely of wood. Because there is was no better solution.
But the wooden gripper is not performing well enough. A new design is now necessary. Considering the gripping mechanism it would be ideal to use metal. Its resilience would be great. But the gripper is relatively complex. Building it in metal would increase the part count significantly. We are also redesigning the gripper to be able to operate in both the vertical and horizontal planes.
Due to the complexity of the design, additive manufacturing has become the go to.
Let me be clear. 3-D printing is very often overused. It has become a fad rather than a practical tool. There are very specific applications for additive manufacturing and they are not far reaching. 3-D printing is not very scalable and the quality of the parts is not terribly reliable. But in this case 3-D printing is the best solution.
So, I would like to introduce you to Version 0.4 of Jerry's new universal 3-D printed gripper.
Here are a series of demos that we did with Jerry to show off his physical capabilities. Jerry is still operating by remote control but software will be completed for several of these tasks soon. Either way it is always cool to see a robot getting you a soda, or vacuuming the floor.
So how are we going to go about letting Jerry get a soda autonomously. Well again he has the capability already he just needs taught. There are several major motions that Jerry has to meet so let's break those down.
First, any robot that is going to get something from the fridge has to open its door. (We've already got the identification of the fridge, that is easy) Normally, a robot would be designed with a 7 DOF arm that is able to open a door without the robot actually moving. Since Jerry has such a limited arm that is not an option. In the video you can see that Jerry has to use his whole body to swing the door open. This motion will not be that difficult to achieve autonomously. Jerry is able to track the edge of the door very easily. He also has a general knowledge of the location of his arm with respect to that edge. This is where our mechanically adaptive design, or the slop, in the arm is useful. What we will likely do is have Jerry track the edge of the door and its motion and then have him move his arm along the projected path of that motion . But as the door moves to a new location he can update that projection. This is not a precise method. But it will be effective and his arm will stretch and bend a bit to allow for it to occur. So, so put it crudely, instead of grasping the handle precising he basically lassos it with the gripper and gives a jerk then continues jerking.
So we have the door open. Based on what he is retrieving he will have to do an identification. We plan to rely on a basic database of objects and the owners actually training Jerry when he arrives. He will know what a tupperwear bowl is and certainly what a can is. That is all proven and we have the code running for it already. So he identifies the can and again uses his entire body to move his gripper to the location. Again we don't rely on precision. Jerry is going to push right on past items that he is not after. However we don't want him to jerk out all the items in front when he pulls out a can from the back. This will be difficult. But in order to simplify it a bit we will likely have him blaze a trail on the way in to the item he wants. Then he can come back out. Honestly this is an equal action to a human. When we want a soda we are going to get to it. And we will mess up the organization of the frdige to get it.
As far as bringing the item to the person Jerry can just retrace his steps from where he began. Really the most difficult component of this task it to have Jerry open a door. Our solution is sloppiness. We are building a robot that take some abuse and adjust mechanically in order to eliminate processing. Unlike in an industrial setting where a chip has to be placed at great accuracy the human world is designed for uncoordinated humans, so our robots can be uncoordinated also.
Today, if you go looking for a robot to use in your house you really only have a few options to choose from. The first type of product is a single task system like a vacuum that is really more of an appliance. Another option is to get something that is basically a smartphone on a stand. It can move and interface with smart appliances in your house but really can't do anything your phone can't. The last choice is a robot for the sole purpose of entertainment. These machines are meant to be friendly and interactive thus replacing a dog (or friends). The Jetsons-style home robots that cooks dinner, does the wash, and has an attitude does not exist at a commercial level.
So why isn't Rosie in our kitchen yet? Well a big part of it is cost. The robot that is closest to what we imagine as a home robot is the PR2 (personal robot) developed by Willow Garage. The PR2 has two arms, each with a human-like 7 degrees of freedom and can roll around. It is outfitted with dozens of sensors and has the capability to do just about anything. But the PR2 costs 400,000 dollars.
The cost of the PR2 is due to a couple of reasons. The first is that there is no economy of scale. Since its introduction in 2007 there have only been a few dozen or perhaps a couple of hundred made (no actual numbers have been released). With such a low volume, but still needing to pay salaries the margins on robots like the PR2 are necessarily huge. But note that the markup is not so great that the robot would be affordable if it were sold at cost. PR2s for education have been released at as low as $150,000 which is very likely near the cost of the robots. So it is reasonable to assume that on the low side the PR2 costs around 100,000 dollars, in parts, to make. And since there is still the time and effort of assembly, that number is likely higher. Now why is that price so high? The answer is robots are machines not computers.
Robots are composed of motors, and gears, and magnets, oh my! Physical materials such as these have a floor price that they may achieve based on limited supply. Unlike chips, magnets do not get exponentially cheaper, because we can only extract and process so much neodymium. So even with an economy of scale, robots will be expensive due to the cost of raw materials. Looking at the PR2. It has two arms, each with seven motors and the grippers. Then there are the four drive wheels and their articulation. As well as any other actuation for sensors. Those components, which are high performance, along with the gearboxes and other custom mechanics could easily run up to around 50,000 dollars. And that is before the sensing and computing are installed, which, though getting cheaper, are still expensive.
Essentially, robots are expensive because they are currently custom, high performance machines. Slant built Jerry to be practically the opposite of that. Jerry is designed to be manufactured affordably by a guy in a garage.
The first step we took in this direction was to make Jerry out of wood. Wood was an ideal material because, not only it is beautiful and affordable, it is a simple material to train people to work with, so skilled labor can be used affordably until a factory can be made.
Jerry addresses the primary issue of motors by reducing them. He uses a basic differential drive system that allows for effective locomotion with only two motors. The arm actually only has two degrees of freedom and a gripper. But the design is efficient enough to give Jerry a work space, from the ground to his gripper, 38 inches high. The arm is able to move up and down as well as forward and backward. Any side-to-side motion can be performed by his drive wheels. This system is a bit more complex than a 7 DOF arm as far as software is concerned, but it was simpler mechanically. and since mechanics are what causes the cost to the customer that is what we focused on.
Additionally, Jerry is minimalist on sensors. He relies almost entirely on his vision system to perceive himself and the world. This was chosen because vision has the capability to provide all the information that could be needed about the world as long as a computer is powerful enough to glean that information, which they are.
Jerry has been designed to be affordable through reducing expensive mechanics and replacing it with cheap computing. All this has resulted in a robot that is capable of any number of tasks and will cost around $2500. So now you have an option of buying a robotic swiffer for around $400 or getting a true home robot that can grab a swiffer, walk the dog, monitor the house, and any number of other things for $2500.