edumip balance code filter coefficients

I was hoping the creator of rc_balance.c for the edumip robot could share the model used to determine these filter coefficients

// inner loop controller 100hz
#define D1_ORDER 2
#define D1_NUM {-4.945, 8.862, -3.967}
#define D1_DEN { 1.000, -1.481, 0.4812}
#define D1_NUM_LEN 3
#define D1_DEN_LEN 3

// outer loop controller 100hz
#define D2_ORDER 2
#define D2_NUM {0.18856, -0.37209, 0.18354}
#define D2_DEN {1.00000, -1.86046, 0.86046}
#define D2_NUM_LEN 3
#define D2_DEN_LEN 3

I’ve made several balancing robots but I’ve never done it with this kind of filter and I would like to understand it a little better. How would I determine new numbers for something with a bit more mass?