Emerson Electric wants to own Rockwell Automation, and over the last three months has made a series of offers to that company, according to people familiar with the situation.

Emerson's most recent offer for Rockwell, worth more than $27 billion, was in early October for $215 a share, split evenly between cash and stock. Like the $200 a share offer in early August and one a few weeks later, Rockwell gave a terse rejection, according to people with knowledge of the correspondence.

Rockwell Automation shares were up 12.7 percent at the opening bell in response to CNBC's report. Emerson Electric shares were fractionally lower.

An Emerson official confirmed the company has made recent offers to purchase Rockwell, but would offer no comment beyond that.

Rockwell, a fiercely independent Midwestern company with a relatively new CEO, has been no stranger to Emerson as that company has looked for opportunities to consolidate in the industrial automation sector. But after years of trying to engage with Rockwell, Emerson for the first time made a formal offer to buy Rockwell in August. That offer was for $200 and when met with rejection, Emerson came back with both a higher price and with concessions on social issues that it hoped would bring Rockwell to the negotiating table.

The effort, which included a willingness to rename the resulting combination Emerson Rockwell, has been met with continued rejection. In addition, Rockwell's stock price has moved up by more than 13 percent since Emerson made its first offer.

The latest offer for $215 in cash and stock valued Rockwell at over 20 times its expected earnings before interest, taxes, depreciation and amortization for 2017 and roughly 32 times analysts EPS estimates for this year. It would have a total value of more than $27 billion.

Emerson's offer stems from its desire to be a leader in all areas of automation and to present a stronger competitive offering to industrial companies as European giants such as Siemens, ABB Automation Group and Schneider Electric become more aggressive in the field.

Emerson believes the combination could bring capitalized synergies worth $6 billion.

It is unclear whether Emerson is willing to mount a full on hostile bid for Rockwell, which is incorporated in Delaware.

Rockwell confirmed later Tuesday that it had rejected the two unsolicited proposals from Emerson, noting that the board of directors had carefully reviewed both offers and determined they were not in the best interest of shareholders.

Sources close to Rockwell tell me the company's rejection of Emerson stems from a number of concerns including what they say is Emerson's inability to successfully integrate previous acquisitions. The sources termed the bid a "Hail Mary" from CEO David Farr as he "struggles" at Emerson to move more firmly into automation.

Rockwell has a staggered board of directors and no ability to act by written consent to call a special meeting, making a hostile approach more difficult.