used for HBot or Corexy.

Set arm_solution to corexy or hbot in config, for example, add this line to your configuration file : 

arm_solution      corexy

Then uncomment corexy_homing in config if using homing

Also it is recommended to set

alpha_max_rate
beta_max_rate

to the top speed your steppers can go, as these refer to the actuator speed (the X and Y steppers) which on a corexy can run nearly twice as fast as the requested Cartesian speed when gong in certain directions.