There are mostly two kinds of attackers: the automatic, and the targeted.
Automatic attackers are not humans; they are infected machines, part of various botnets, which try to expand their basis by finding other machines to infect. Their strategy is mostly random: they try random IP address for an open SSH server, then try common passwords for common account names. There is little you can do to increase (or, for that matter, decrease) the amount of connections of this kind you will receive per day. Some network providers try to detect these occurrences and block them or limit their rate, so you could speak with your provider and see if he has such systems in place.
Targeted attackers are humans who want to crack your machine, specifically. To get that kind of attacker, you need to provide some sort of motivation. You could try to boast about some desirable "goods" stored on your server (e.g. tons of pirated copies of gams or music or movies), making it worthwhile to hijack your machine. You could try to host a political-oriented blog with highly controversial positions. Sometimes boasting will by itself attract attackers: everybody loves to shut up an insufferable know-it-all, and hacking his server looks like an efficient way to achieve it. In short words: make some enemies.
Note, though, that brute-forcing passwords is the lowest grade of attacks. If some of your newly acquired enemies are a bit competent, they will try other kinds of attacks, such as exploiting vulnerabilities in your software. Also, some of them could think "out of the box" and not target your server, but you, directly; for instance, if they look up the name of a domain you own, they might obtain your address or phone number, and pay you a visit in person. As a general rule, I advise against making enemies. There is no such thing as "consequence free"; there is only "improbable consequences".
If that is for research, then you could try to approach the sysadmins of some major sites or infrastructures. This is your senior project: therefore, there is potential academic support. With the help of your professor or advisor, you could try to see if an ISP or a big hosting service would agree with collecting data on their system; they might even find some fiscal benefit in collaborating with a scientific project. Alternatively, most sysadmins are addicted to Guinness, and may agree to help a co-drinker, especially after the third pint (your profile state that you are 17 and live in the US, so this solution cannot officially be workable for you).